Its hard not to feel like a little kid in a candy store when people are looking to build a brand new great gaming pc. So many things from so many people coming from so many directions. My suggestion is for you to sit down and look at the PSU buying guide and determine what you want to do with the pc and go from there. Choosing a PSu will depend on so many factors like sli or not, how many peripherals you have, the mobo, the amount of ocing you want to do and many more. If you think the PSU is overkill it prob isnt. This might be the funnest and yet most frustrating part of trying to piece together a system.
2) Next determine the CPU that you want. The 4400x2 or 4800x2 are both awesome choices and will make you happy.
3)Next, Mobo's. The ausu you picked out is a great one that many like, compare it with a few others like a DFI sli board and see what fits you best.
4)Video cards are always evolving so its always such a hard decision to make. If you want to do 2 cards lsi then i realy suggest you get one card first, the 7900gtx is a wonderful card that blows everything away. Having the sli mobo and the one card will allow you to upgrade later. Theres not point in trying to put all your eggs in one basket and allowing no room to step up later.
5)RAM, 2 gig of some good OCZ or g skill ram will do you fine. Make sure it has some goos timings. If you havent oced much and arent the decerning ocer then I doubt you will notice much aof a difference from the high end ram to the extremely high end performance ram. Im not saying buy value RAM, you really cant go wrong with OCZ, g skill, or even some nice Corsair XMS memory.
6) Hard drive. Get a 74g WD Raptor HD because its the top of the line gaming HD with plenty of space and wont be a weak link in your system.
7) Colling, Big typhoon period for air. Wait to water cool.
8)Case. You cant go wrong with a lian li -65 or thermaltake like was mentioned earlier. Oddly enough thats what im going for this week to get some nice air flow going
They may be plain looking and a bit more exp but a crappy case is embarassing, im living proof.
Take it from me 3 months ago I was using a 1ghz P3 to surf and roll on WoW on lowest settings. I got in a hurry to get what I thought i wanted and prob coudl have gone alot of different ways and maybe made a better system. Of ocurse I got lucky and guessed alot on my order and came up a winner with a nice oc and great temps but it doesnt work out that way all the time.
Sorry for the long post but I really hate to steer someone in the wrong direction with such a big purchase. Gl and do some panning and dont rush it, Youll be happy.