PcNubNub :
I have a Core 2 Quad 9550 and acer G43T-AM motherboard.
Will a GTX 750 work??
Ofcourse it will work. Your motherboard has PCI-E 2.0 x16 interface.
GTX 750 has supports PCI 3.0 ,2.0 and even 1.1
You won't loose any performance at all. Right now only few cards can actually use more bandwidth than what PCI-Express 2.0 can offer (meaning they need to be on PCI-Express 3.0). GTX 750ti is not one of them, so don't worry, you will loose zero performance.
Just make sure that you have a suitable PSU. NVIDIA recommends 400W to 650W PSU