Stickroad - Seeing as he can afford it I see no reason why he can't swap for some more expensive/reliable RAM. Thinking G. Skill HZ PC6400 here as it will clock to 1100MHz easily and is very reliable compared with the record on the Ballistix.
I would also change the mobo for the P5K Deluxe for the performance increase & swap the cooler for the Tuniq so it will fit on.
Still in budget and more peformance and reliablity + free wifi
TBH for a gaming PC I would get the dual core atm seeing as it runs cooler and will give better clocks which would be an increase in gaming performance. Seeing as the lack of 2+ core support in games. Seeing as its a P35 chipset then you can upgrade to a Peryn when they come out if you save on the CPU now.
4gb of RAM will limit your OCing potential and is not really needed unless your running Vista 64.
SLI REALLY isn't worth it atm.
This would be my spec - which leaves £360 spare when the new CPU's come out for when games will actually use 4 cores or more and when the CPU's run cooler and faster
Edit: In response to Gee's above spec - Don't get that mobo AGH its nasty and picky with memory.
The cooler won't give you a decent OC especially not with the Quad Core and the memory won't clock too good either.