lol,
ok, with the phenom build get a £100 dfi board, and a£40 pack of 4gb mem.
Then add on 3 extra gigs for the i7 build as 3gigs will cripple you in many games. GTA4 with 2 gigs is a joke tbh and 3gigs won't be much better. I simply wouldn't build a computer with less than 4gb memory now or in the past year, and that means going up to 6gigs on i7. When you run out of memory in a game and start paging to the hdd constantly the phenom rig with more memory will easily outperform the i7 rig, its that simple.
So in reality the phenom entire build is £400 and the i7 is closer to £600 with more memory. In that case, considering either build once enough mem is in will be the same speed in gaming, I'd go the cheaper route. If you do video rendering for a living, the £200 extra is well spent, if not, don't bother.
EDIT:- I just realised why those Gigabyte boards are cheap, 4 dimm slots(for triple channel, in all honesty not a clue how that works, 4th dimm slot just so its the same design as previous boards so less reworking, not really functional 4th slot? honestly don't know). either way, its still "just" ok as you can obviously go 3x2gb sticks rather than 6x1gb sticks, but does certainly limit future mem upgrades though I'd suspect 6gb would last you for a couple years. Though if you're a renderer/PS user more memory might be wanted and that becomes a serious problem. If I were going top end i7 I wouldn't skimp on a budget mobo that has limits, which would again add another £70 onto the price.