Yes!
If you compared those two systems, you would see a significant difference, though it would depend on what you were comparing it with.
A 2Ghz CPU is not likely to "bottleneck" a 6600GT, but a faster processor is much better, as the CPU does alot more than the video card (generally)
Your PSU makes no difference(sort of), if you meet the requirements, then your system will run fine, if it does not, generally your video card or PCI devices will be disabled (in the case of AGP, your display will be set to 2-bit colour and a res of 640x480)
The main reason a kick ass PSU is wanted these days is because more and more people are overclocking and using more power on more power hungry devices, a 2 or even a 3Ghz CPU and a 6600gt should run fine on a 400w PSU
Basically, its a tricky question, stock standard, no, your CPU should be running fast enough to handle the video card, but if you started to overclock that card, your CPU would start to lag behind I think [img]smile.gif[/img]
EDIT: My response may seem a bit strange becasue I say yes then no, I am assuming that you have a 2ghz cpu with a 6600gt, in your case no, in a broad sense yes, your cpu can have a major effect on your video card performance, but there are many, many, many, many other factors that need to be considered, ie, RAM, mobo and so on.
[ 02-07-2006, 08:19 PM: Message edited by: Hivetyrant ]