im currently using a AMD Radeon HD 6700 2GB and have found that it is good with gaming …but for rendering…not so much. So i am researching a new one. What is a reasonable replacement? Would like to find a card that i can enable the option in blender to use the graphic card for rendering instead of the CPU. The card im using does not have that option Thanks for the helpful insights in advance 
There is no question you will be shopping for a card with Nvidia chipset - suggest that you indicate your budget and whether there are any constraints (eg if you have a smallish case and cannot support a full size card). If the budget is big enough and your motherboard / case / power supply support it then maybe a couple of cards!
Cheers
Nvidia cards usually.
A card like a 980 will be good for gaming but below average for GPU rendering,a TITAN is the best of both worlds,a quadro card is excellent for GPU rendering but you probably won’t even be able to play some of the older games with it.
Actually the Quadro cards are not very good for rendering, at least from tests that I have seen. A Geforce card of similar make and model will beat it for both performance and price. Quadros are good at double precision number crunching but most GPU renders like Cycles and Octane use single precision which works better on Geforce. Of course the best setup is to have a Quadro card for display (for the better OpenGL handling) and then one or more Geforce cards for rendering.
To the OP, you might find the 970 to be a good choice, it’s around $300 and is good for gaming and for Cycles.
Version 2.73 is supposed to work well with the GTX 980, according to advance information.
But any nVidia GTX series card will allow you to use GPU rendering.
Also, if you have two full-length slots on your motherboard, you can use two cards and they don’t have to have the SLI connector for you to use both with Blender.
guessing you are using MS WINDOWS
( if linux you should know how to install the .run or rpm or deb)
guessing windows
for nvidia REMOVE!!! the microsoft AUTO install opengl disabled driver that “auto update” wil lAUTO install
MS has disabled most OpenGL things
install the nvidia driver FROM THE NVIDIA WEB SITE!!!
http://www.nvidia.com/Download/index.aspx
but
before you do buy a new card
grab tha AMD/ATI driver for your card FROM!!! ath AMD web site
and uninstall ( in safe mode!!! ) the Microsoft provided driver ( it to is opengl disabled)
then install the driver FROM AMD
http://support.amd.com/en-us/download
if he is running a 6700 its probably a prebuilt pc, hp, dell etc…he probably has a 300 - 400w power supply which is going to severly limit the cards he can use. it probably has to be fully powered with the pcie rail without any pin connectors.
see what your power supply is. if you put in a card with a higher min spec than your pc has you’ll be even worse off after spending the money, your pc will just crash.
a gtx 750ti is probably the most you can put in your pc without changing the power supply 1st.
A bit more background: According to the specs posted on the nVidia website, the 980 only uses 165w compared to 250w for the 780.
Just something to keep in mind when calculating the size of power supply required. 
true ron but the min for any 900 card is over 500w, thats why i said 750 not the 780. the 780 requires a 600w. any 900 card, espicall7y rendering where usage hits 100% and stays there, is going to pull so much power it crashes his pc. i doubt his psu even has a 6 or 8 pin connector. i think the rail has a max power of 65-75w which is what he’s probably restricted to. any 900 carrd will require over twice as much power as he has. chances are he wont even be able to instal the card due to no pin connectors. the 6700 car he has runs at about 35 watts. there is a reason they didnt but even a 6800 or 6900 in the machine. no extra power connectors. pc makers for some reason wimp out on the psu which is one of the cheapest components. they give you lots of slots, but no power to really use them. they’ll sell you an i7 pc with a power supply so weak even over clocking it will be too much.
every card above the 750 requires secondary power, more than just the rail. even the 760 requires a 500w supply and 6 pin connector. you dont have to calculate the power required, it’ll be listed under min specs required for the cards. if he is going to upgrade his psu he should go for more than the minimum he needs to futureproof his his computer. the difference between a 500w and a 700w is probably going to be about $20. but i guess wile4 getting a real pus is only $20 to us, but if you are going to sell a million pcs its 20 million to them rather than just the difference between $500 and $520. and nobody ever asks about psu. the want to know what cpu, how much ram, hdd capacity, etc…they never ask how its going to be powered. if cars were made by pc companies they would come with 2 gallon gas tanks.
it irks me when i take the shell off a pc and wonder what they were thinking. why give you the slots to put in more hardware but no way to power it. they just tease you.
Just wondering…If in my next computer I use 2 cards Is there anything I need to do as far as setting up in the cmos or whatever it is for the computer to use 2 cards? Also Does that acutally mean you can render 2 times faster then the 1 single card?
just follow the manufacture instructions. it will render almost twice as fast but not twice as much. you basically have to copy the ram from one card to the other so if you have 2 gigs of ram on each card you can render a 2 gig scene twice as fast but you still wont be able to render a 3 or 4 gig scene. they should give you an sli jumper to connect the two cards.
SLI mode is bad for renderers, it uses memory and slows the render down a bit.
my power supply is a 500W and my card is connected to power with a 6 pin connector. My problem was in my first model i added very heavy textures on every thing…took forever to render…now ive eased up on the textures and started using basic colors. I do want to upgrade my card so it can do the rendering on it instead of the CPU…only have 4 cores…it does ok…bout an half hour to render what i have now
that has to be like a 6790 then. looks like the 760 and the 970 will run on a 500 psu. not sure which is the best for rendering. the 780 ti is better than the 980. there is a 760ti that is an oem part. it’ll be hard to find but may be worth the trouble. and pick a brand that has a great warranty. some evga cards have a 10 year warranty. that way if you burn it out you get it replaced free. for a single card it looks like the 780ti the best card for cycles, will run on a 600w power. just look on ebay for prices THAT WERE SOLD and see if you might want to upgrade your power supply and go for a top card if you can get enough for your used 67XX and power supply. never look at asking prices, alot of people keep the item because it doesn’t sell. when selling prices always look up items that actually sold.
if you do decide to upgrade your power supply and go for the 789 ti it could be worth waiting a few months. currently the 780 only come is a 3 gig version. there is a 6 gig version but they wont release it until their titans are sold out because nobody would buy the titans. (the 780 actually beats the titans and is half the price) but amd are releasing the 390 soon which will force nvidias hand even if the titans aren’t sold out. the gpu ram is your hard limit including cycles render engine. if cycles keeps getting bigger/more complex/more features it will leave you less memory for your render unless the microkernals start working in which case amd video cards will work too. you’ve probably read the “good news for ati” thread. but for now more memory is better.