I am looking for a new GPU for my Mac Pro, but only found ATI Cards so far. I would like to buy a card with at least 1 GB Ram and maybe CUDA support for Cycles. The only card I found is the QUADRO card from nvidia, but it costs a pricy 800 Euros at least. That’s to much for by budget 
Here is what I found so far:
ATI and NVIDIA at cyberport.de
ATI at Amazon
IF you find any affordable options for either ATI (Open-CL) or NVIDIA (CUDA) or BOTH (on the same card!?!) PLEASE let me know…
I’ve been a loyal/fanatic user of Mac computers for over 25 years, but the recent “disavowal” of the MacPro tower “workstations” (not exactly!, considering the lack of GPU options, eh?? :-? is really making me nervous. I have a mid-2010 6-core 333Ghz “Westmere” Xeon/Intel chipset, and the “stock” (best…only?) AFFORDABLE graphics-card Apple offers… Their only NVIDIA card is well over $2000. for the Quadro with CUDA… which seems WAY overpriced for what you actually get…
ALL the hardware “players”, NVIDIA, APPLE, ATI, INTEL all seem to point their “finger” at “the other guy” and play the “blame game”… Meanwhile the end-user (you & me…) get stuck “out in the cold” with no viable options, and a SERIOUS lack of sufficient technical information on (I’ll call it…) “Adaptability options”…
Is/are ATI Radeon cards “upgradable” (flash the on-board instruction set? I’ve heard you can do “something similar” on NVIDIA cards, sometimes, to make them “more compatible” (or DESTROY THEM, if you make a mistake…)
OR, is a “simple” driver-software update/upgrade possible? (if so, WHEN!!??? :-///
I wish I knew definitively what was going on, and what to do about it… (& please don’t say “junk your Mac”… it’s the only computer I have, or can afford–have to consider replacing it in a decade or so… I’m not rich! 
I would consider “dual booting” my Mac with a spare hard-drive with (probably) UBUNTU on it, but I know NOTHING about Linux, and no idea on setup or compatibility/configuration of “hardware” (presumably more NVIDIA card options for Linux??? driver-software???)
Lack of solid information is CRIPPLING!! Please (anybody!) advise!
Apple is always looking for the best solution for its own balance, not yours; that’s why on a 1000$ machine you only get an integrated VGA with shared memory.
Don’t be a fanboy and get an high end machine with a GNU/linux distribution, you will be surprised; Apple is not about technology, it’s about money more than the others brands.
Keep in mind that Cycles right now is still under development and it does not even have even an half of the features which is supposed to have, also the “CUDA version” is incomplete compared to the “CPU version”, it’s true that OpenCL is simply not supported in Cycles, but also CUDA is not fully supported too, at least right now.
If i was in you i will not buy a new card for another 2 simple reasons:
for more info about what you can get for your budget try reading the monthly article on THW