AMD uses dual channel RAM, so you would need to get a kit with either two or four DIMMS, not three.
For sheer speed the i7 wins over the AMD line hands down. However, the Phenom II line is no slouch, either. £100+ is like $200 in the US, plus you will save some dough by going to 4GB of RAM. These look good (G.Skill are awesome)
G-Skill 4GB (2x2GB) DDR3 1600MHz/PC3-12800 Ripjaw.. | Ebuyer.com
£100.00 (-£20 right there)
I would go with a quad instead of the x6 (unless you are doing some serious transcoding or such). The 465 Black Edition (unlocked multiplier) is a very nice CPU.
AMD Phenom II X4 965 Black Edition 3.4GHz Socket AM3.. | Ebuyer.com
It looks like the mobo is what is going to make the biggest bank.
Basically it comes down to how much you want to spend, mate. Any of them will give you great performance.
EDIT: Oh, and good to see you back around.