Yeah. If your going for best bang for buck, then it's the 4850. If your going for the best gaming system, it's either the 4870 or the 280. But the 280 is waaaay overpriced compared to the ATI counterpart.
Ok..
well I saw they had Corsair Ram 4 Gb sets. I'd go for those.
The best PSU I saw there was the 750watt Toughpower. That will do for the rig, and have a little headroom for upgrades later.
The Mobo I'd say go for a Gigabyte X38 or X48. Those are solid boards that have Crossfire capability if you ever want/need it.
For HDD's I go for a 74 Raptor, then a WD 640Gb drive. Those drives have 2 320Gb platters, which basically means they are damn fast!
That's just my two cents