If you have an aftermarket cooler on your CPU already get the Phenom II, that's a really good CPU at that price. If you only have the stock cooler that came with the Athlon, then think *very* carefully as it will probably struggle to cool a Phenom II and you'd need to get a decent aftermarket cooler as well, which would push the price up (still a good deal though, IMNSHO).
If the choice is more memory
or the new processor, get the processor as (again IMNSHO
) going from a 2.2GHz dual core to a 3GHz quad core will make more real world difference than going from 2GB -> 4GB: I've only seen a computer ask for more than 2GB RAM when Chrome is playing silly blighters with it's VM usage! Of course, if you can afford both upgrades then the more the merrier
Definitely avoid 1080p with the 512MB 5770: it wouldn't be completely happy at that res. The real question is do you want widescreen or standard aspect, and do you want VGA or DVI. For less thasn £100 you aren't going to beat the digimate that CAT's already linked to, but you can get cheaper screens at 1280 x 1024, 1440 x 900 and 1600x900. Avoid any of the 18.5" / 19" widescreens at 1366x768: I've heard quite a lot of bad things said about them and the only one I've had the displeasure of dealing with was pretty poor...