OK, I've ordered the Q6600. The fact that all you (helpful) people are able to debate/argue over them, proves to me that they are all (for me) very similar and are all viable options.
So my final order was a...
Intel Q6600
Gigabyte GA-EP43-DS3L
2GB Corsair 1066MHz RAM
Corsair VX-450 Power Supply
Thank you for all your help.
On another note, someone told me today that OEM Windows is licensed to the motherboard. I have OEM Windows XP on my soon-to-be-upgraded computer and I intend on keeping the hard drive. Since I am changing the motherboard, does this mean that Windows will not recognise my computer as being licensed?
Also, I have a really old/bad computer (5 year old Celeron, 512MB RAM, GeForce4) that I plan on adding my AMD 3500+, old Motherboard and old RAM to. However its hard drive is a IDE hard drive, and the motherboard only supports SATA. Is there some sort of adapter I can buy that I can simply plug my hard drive in one side and my motherboard in the other and they'll all play nice?