Personally I would opt for the second cheapest GTX 950 in my list above; assuming you have at least a 400 watt PSU and your case is long enough to fit the card.
Best to do it right!
GTX 960 Ti 4gb - EVGA - $220 approximately - This is only a 120 watt card - so you should be good with a 450 power supply
Your best bet is to go big - always. You don't wanna buy a GTX 950 to play Deus Ex Human Revolution
only to find that you can't play the sequel Deus Ex Humanity Divided this year because you fell short.
GTX 960 Ti 4gb - EVGA - $220 approximately
4 Gigs of Vram will keep you gaming for a while - EVGA has a good product
Oh Yeahhh !!! Cheapest Though - that is the question ..........
GTX 750 Ti 2GB Version .......is your direct answer It sells for about $125
Only 60 Watts - any 300watt Pwr Supply can play this card - and it's a good card.
Nuff said Your choice $120 GTX750Ti2GB or $220 GTX960Ti4GB ?????????????
Look in your wallet and make a choice