1. The Antec SmartPower PSUs tend to be less well-regarded than the TPII PSUs. The 550W TPII is a favorite here, and it's worked well in my system.
2. Opterons are server-grade (better constructed for stability, etc). If you're not overclocking, an Opteron 170 or 175 would be good, though the latter is more expensive than a 4400+. Really, though, an Opteron 165 is great, much more inexpensive, and will certainly be usable in four years' time.
Judging from the emphasis on sound and video quality, I'm assuming this is primarily a gaming system?
Nice system... I recommend though going for a 4200+... You won't really need all that extra cache (unless you are doing very processor intensive work on it) and you might as well save the money. Also, word of warning... make sure you update the BIOS for the A8N-E as soon as possible... only then will it become nice and stable, and then you can start adding everything else in. I'm not so sure about the nvidia RAID drivers, but i have yet to use them so i wouldn't know. Again, go for an X1900XT, cheaper, gets the job done easily, and can be OCed to XTX speeds if you want that extra performance which in my eyes is not necessary yet. Apart from that, excellent choice in components :wink: .
"I rarely play games, but I would like to have good graphics when I want to play a game. I would also like a good enough card that will still play new games in 3 or 4 years."
If you rarely play them *NOW*, I'd recommend a simple 6800GS in PCI-e instead for about $160; save the other $340 for when you will start playing them... (A 6800GS will play any game out, albeit some of the newest titles are best run without AA/AF)
A 1900XTX installed without gaming is almost.... sacriledge! :-)