While I agree that the Corsair 520HX is a better PSU (I own the 620 and its a seasonic rebrand) for that this guy is using it for (and no OCing or moderate OC) the Antec's are more then fine.
You can save a few bucks getting a 256mb video but with Vista and DX10 I would say that you want to get as much ram on your video as you can afford, IMHO for a few bucks you can prolong the life of your card a bit.
I would get the Wintec Ampo sticks instead (look for the reviews here) 3AMD2800-2G2K-R which are rock solid. Upgrade to an 8800GTS 320MB, get the cheapest P965 or 650i mobo that fits your needs (I like the 650i's more myself) or come with rebates, and get yourself an E4300/4400 CPU. Stick with the Antec Trio and the $25 rebate or if you're really concerned get the OCZ gameXstream 600 or the Corsair 520HX.
With the ECS 650i mobo and the Antec you've got $45 MIR, sure you'll go over your budget a bit but you'll have a significant increase in performance in your games.