Its going to be a nice machine but i do have a couple of things you may want to consider.
The first thing i want to call attention to is the HDD. You listed a sata drive with a 8MB cache. You may want to see if you can find one with a 16MB cache for the same price. Also keep in mind that the board you listed supports sata300 instead of the standard sata150 which will obviously give you twice the transfer rate with twice the cache to back it up.
Next is memory, your board will support dual channel memory. It may be cheaper for you to buy 1 gig of dual channel instead of 2 gigs of single. 1 gig of dual channel would be plenty of memory and also leave you the option to add another gig of dual when your finances further allow.
The motherboard has integrated 8 channel sound so buying a sound card would be more for show than a necessity. The board only has 2 PCI slots so theres not much room for expansion but it does cover your wireless card and the option of a sound card. The case should accept the board just fine, i dont see any problems with hardware being in each others way.
Have you considered the 6800 nvidia cards? They are a little cheaper than the 7800 and still offer unreal quality and performance.
Thats just things you can think about to maybe help your budget without sacraficing performance. Hopefully it helps




