I'd LOVE to have that system.
A 6600GT is nothing to laugh at. While it can't compete with its more expensive brethren, it has no toruble against similar ATi solutions, even pumping up AA & AF.
However, I wouldn't wonder about getting amazingly good 3Dmark scores (yes, they would be amazing, as I have a 5900XT right now).
Why not spend over $200 on a video card, but spend $1000+ on the rest?
Because the rest you are likely to get mroe use out of.
Encoding audio and video...CPU/RAM.
Office stuff...CPU/RAM/HDD.
Gaming is the only nromal application in which ALL parts matter. It is the ONLY application for which the video card, besides good 2d output and DVI compliance, makes a difference.
Also, the monitor makes a difference. I'm a 17" that can do 1024x768 @ 85Hz.
Even w/ moderate AA & AF, something like a 6600GT will do me fine (hell, my 5900XT is still fine, though I do wish I'd waited out for the 6x00 series) until I find another suitable monitor.
Lastly, I know more than one gamer perfectly happy with crappy as hell video cards.
Friend 1: GF4MX 420.
Friend 2: FX 5500 (no, he didn't pay too much for it, $40+tax).
Friend two had to upgrade because of two things. First, my old GF2 GTS was finally dying (stability, video corruption...it's only on its THIRD heatsink fan...), and that WoW was doing too much texture swapping.
He knows of AA & AF. He's seen AA & AF in action. I offered him my 9600XT for $100, and if he'd wanted it more recently, I would have gone down to $70 (I won't want it to be all money down the drain, but no need to amke money on him). But no. He just needs to get 30-60 FPS at 1024x768, lowest quality all around.
For every person who thinks a FX 5200 is going to rock, there's also a guy who knows very well it its capabilities, and is perfectly happy with it.