Your 8800,is that a 1GB ,or a 512MB ? ..just curious.
I don't know,but i CAN share some experience.
I had a 400mhz,a 1.2mhz,and 2.4mhz PCs on my LAN a few yrs ago...all were maxed with ram.I have alot of dated nvdia video cards laying around,so i eperimented.I was curious if a slow machine would benefit from a fast video card.I started with a 32MB in the 400,then 64,128,and finally a 256 (all cards used the same nvidia driver so it was easy.THANKS NVIDIA !
I installed tiger woods 2003 and went to work.I figured anything above a 32 or 64 would be useless overkill on that ancient 400,but i was wrong.The game ran smoother,and smoother untill i reached my 256 ceiling.
I still have that 1.2,and just installed lord of the rings on it.The game demands a 1.8 cpu min,yet my 1.2 runs it smooth with a 7600GS (512mb) installed.(even though the 7600 wants a 8x AGP slot,and the 1.2 only supports a 4x)
Experiment results say fast video cards are worth it,in ANY machine.CPU's are a distant second in comparison.