I have the same Q9550 CPU on an ASUS P5N-D board
http://www.overclockers.co.uk/showproduct.php?prodid=MB-265-AS&groupid=701&catid=5&subcat=1057 with 8GB OCZ DDR2 PC2-6400 SLI-Ready Edition RAM, 2 x Asus EN9600GT's + CoolinK GFXChilla GPU Cooler (SLI) and it's a solid performer IMHO. With this brilliant cable
http://www.overclockers.co.uk/showproduct.php?prodid=CB-031-AK&groupid=701&catid=48&subcat= my system cooling (CPU Fan, Mobo Fan & 4 Case Fans) are all run efficiently by this board. TBH, my rig is a "Jack of all Trades" rather than a dedicated gaming machine, It's an HTPC, Photo/Video Editing PC (hence 8GB RAM), Gaming PC all in one. In my experience this board is very stable, performs flawlessly in all these tasks but is by no means a top perfomer.
It's well within your budget & you could get some decent RAM with the balance, Corsair & Patriot are very popular with people on the forum but OCZ's 'Lifetime Warranty' offers supurb value.
I agree the above combination (DDR3) would be a sound choice for for your budget, I thought I would just share my experience with the Q9550 CPU on a LGA775 DDR2 board that's also within your within your budget although out of stock at OC at the moment.