The build looks good, but have you considered the i7-860? The hyperthreading might offer you a little more performance for audio editing apps.
The only other suggestion on something to change would be to see if you can find CAS 7 RAM for not too much more. Otherwise, the build looks about perfect for your uses. 650 W is probably overkill for right now, but if you decide to get a gaming card in the future, I'd stick with that PSU.
If you decide to get a gaming card in the future, changing out a new card for the old one is one of the easiest things to do. There shouldn't be any problem with that.
Yeah I did look at the i7-860 but the performance advantage doesn't seem big enough for the money as I'm on a fairly tight budget. I'm thinking if I buy another rig in the future just for web design I can overclock this one and use it as a DAW.
The RAM is something I didn't really have a clue about, I wasn't sure about the real life performance advantages of buying RAM with lower timings is worth the extra money - I've found some RAM with 7-8-7-24-2N timings for a similar price but I'd rather go with Corsair as I'm presuming they're well built and reliable.
If you're right up against your budget, don't bother with the RAM. If you have a little bit of cash to spend, I expect that the i7-860 is going to give you a bigger boost than any other upgrade for your purposes right now. The difference is $80 over here, not sure what it is over there. Not really much else to recommend, the build is pretty solid.