- GTX 750 Ti (purchasable 4 GB around $60 in amazon) Remember you must have a GDDR5 supporting motherboard. It can run GTA 5 at high settings and many other games e.g. (Dishonored 1,2, Assassins creed 4 black flag, Wolfienstein 2, DOOM 4, etc) at high settings.
??? "Remember you must have a GDDR5 supporting motherboard."
No motherboard supports GDDR5. GDDR is graphics ram. The ram the motherboard supports gas no bearing on what dedicared GPU you can install on a system. All the video card really requires of the motherboard is a compatible slot.
I would not call a 750ti "amazing" its a 2 generation old entry level gaming card. It will run GTA 5 but the settings are going to depend on the resolution and the desired fps.