What is currently the fastest for Cycles GPU I can buy?
GTX 1080 or Titan X? Or anything else?
Titan X, according to specs, has more cuda cores, but does that really mean it renders faster?
How much faster would this card be than my GTX 750 ti, which is quite too slow for my needs at the moment.
Using Windows 10 here
I would definitely recommend the Titan XP. It is very fast and has a large amount of VRam.
Titan XP is the best price/performance option if one includes the quadro lineup(which generally speaking… one shouldn’t).
It’ll be somewhat faster than a 1080, but have much more vram which is really very useful.
There is a benchmark thread in the Blender and CG Discussions section that you can search through for other answers.
All benchmarks seem to be in favour of GTX 1080, but I don’t see anything about Cuda rendering… hmm…
http://gpu.userbenchmark.com/Compare/Nvidia-GTX-Titan-X-vs-Nvidia-GTX-1080/3282vs3603
Titan XP vs GTX 1080
http://gpu.userbenchmark.com/Compare/Nvidia-Titan-X-Pascal-vs-Nvidia-GTX-1080/m158352vs3603
Hmm… Really good performance and Titan XP seems to be the winner (Though not sure about Cuda rendering), but not 3x the price good, I don’t think… 
If we’ll cap off the budged at ~1k Eur.
Is GTX 1080 the winner?..
For 9xx series, 970 and 980 Ti were the best in price/performance ratio.
I’m not sure (I have not been able to see many benchmarks), but maybe with 10xx the same thing happens, and 1070 (one or two cards) have better price/performance ratio than 1080.
I can guess that a 1070 would be around 3 to 5 times faster than your 750 Ti.
Oh - forgot to mention: The 1080ti is being announced in about 3 hours.
If it does indeed have the 12gb of vram as rumoured then it will certainly be an interesting option
I’ll wait for the 1080 TI
Seems like a good option.