New budget build, opinions?

[SIZE=3][FONT=arial]We’re aiming to build something that’ll let us play at high-ish settings at 1680x1050, for under £400. This is what I’ve chosen so far:[/FONT][/SIZE]
[ul]
[li][SIZE=3][FONT=arial][FONT=arial]Intel Pentium G840 2.80Ghz[/FONT][/FONT][/SIZE][/li][li][SIZE=3][FONT=arial][FONT=arial]Gigabyte GA-P61-USB3-B3 H61[/FONT][/FONT][/SIZE][/li][li][SIZE=3][FONT=arial][FONT=arial]Novatech Powerstation 400W Modular[/FONT][/FONT][/SIZE][/li][li][SIZE=3][FONT=arial][FONT=arial]Samsung Spin Point F3 500Gb[/FONT][/FONT][/SIZE][/li][li][SIZE=3][FONT=arial][FONT=arial]MSI GTX 550 Ti[/FONT][/FONT][/SIZE][/li][li][SIZE=3][FONT=arial][FONT=arial]Novatech Prowler Midi Case[/FONT][/FONT][/SIZE][/li][li][SIZE=3][FONT=arial][FONT=arial]Patriot Gamer 2 4GB (2x2GB) DDR3[/FONT][/FONT][/SIZE][/li][li][SIZE=3][FONT=arial][FONT=arial]LG DVD/RW[/FONT][/FONT][/SIZE][/li][li][SIZE=3][FONT=arial][FONT=arial]Total £344.89[/FONT][/FONT][/SIZE][/li][/ul]
[SIZE=3][FONT=arial][FONT=arial]I’m just looking for some opinions before I order this, we have £55 reserved for keyboard/mouse, but we’d probably be able to shuffle some parts around. Thanks[/FONT][/FONT][/SIZE]

The build seems fairly thought-through. Did you already consider ATI video cards? They usually offer more bang for the buck (surely - case by case and range by range, but still definitely worth consideration)