I can run crysis at all very high details with a few even higher and a couple of key values a little lower than very high and the system in my sig averages near 30 fps...which is a highly acceptable framerate for the crysis engine to be viewed at.
you may want to check out the 9600gt as a filler card temporarily until the GT's come out later in the year.
In all honesty though, you'll get spectacular eye candy even with an 8800gt.
If I were building a new gaming machine right now, I'd put all my money into the actual system and get a buget card. It's what I did back last march when I built the one in my sig. I had everything with a $100 7600gt card temporarily until the 8800 ultra oc's were down in the mid $400's and I got one then.
Now, I'd swing for the E8400, and a mobo w/single pcie 16X like the intel boards like the asus p5K deluxe, Abit IP35 pro, Asus P5E LGA or maximus formula (any board in the $200~275 range) with DDR2 support..
and then toss one of these in.
Unless you feel like just overclocking one of the lower speed ones
But yeah, IMO, there's really no real reason to get the 9800GTX right now. It can't run crysis THAT much better than an 8800 ultra so why pay more? There's a very real noticable point of diminishing returns right now in the video card market. Consumers are marking a card's worth by it's crysis frame rendering prowess and a $560 9800 GX2's high res performance just isn't worth the price tag and the 9800gtx can't put up better benchmark numbers than a meager 8800 gts.
So, in my honest opinion, holding out for the new GT's later in the year is the smartest thing you can do with your money. Now just isn't the time IMO to upgrade much, if anything if you've already got a half decent rig.
Anything scoring above 10,000 3dmark06 is perfectly adequate right now. (to me at least)