I suggest getting another processor, like the 4600+ (although you can overclock the 4200+ to 5000 by getting a new... Don't know the english word, the thing that makes wind on the processor ^^)
That'll cost you like only £10 more I think...
Also, there's no need to get a SLI motherboard if you don't get SLI graphics... That'll cost you less money.
Sth else again, I would suggest going with the latest technology, like the AM2 socket and the DDR2 SDRAM...
EDIT : Lol, just noticed the 8800... Well then you should seriously get more powerful processor, if you want the best performance there is...