Case: 5/10 - It will fit the components, but thermaltake stuff is pretty low quality and tacky most of the time. What looks good in a picture isn't always so satisfying in real life. Recommended alternatives: Cases are personal preference I will admit, but viable alternatives in this area include the Antec Three Hundred and the Coolermaster Elite430, available from cclonline.com
PSU: 0/10 - Positively dangerous. Units like this can't even provide half the rating they say [they are not tested against their own maximum rating, the sticker is simply affixed at random] and when they fail because people expect them to do so, they go bang, which damages components, electrics, and can even start fires.
Recommended alternatives: Corsair VX 550W, available from cclonline.com
RAM: 10/10
GPU: 9/10, assuming it's the standard reference design.
HDD: 4/10 - Good drive, but completely inappropriate for storing windows. These are data hard drives, perfectly adequate for storing multimedia, but not acceptable for installing programs or games to.
Either get an additional drive, or replace with a WD1001FALS/WD1002FAEX, which are the high performance equivalent.
Motherbord: 3/10 - Asus stuff, for the last few years is terribad. You'll be lucky if that £155 board lasts more than 6 months.
CPU: 5/10, depending on what it's for. For gaming, the phenom II X6 is a poor choice, as no game can currently make use of its 6 cores, and without all 6 cores being used, the X6 is actually a pretty slow CPU, it's no faster, per-core, than the X4 955, which in turn is wildly outclassed by the Core i5 760 which is actually cheaper by quite a considerable margin.
For programs that can specifically use all 6 cores all of the time like video encoders and 3D renderers, the X6 is not a bad choice, but realistically I'd say replace the board and the CPU you've chosen with the Core i5 760, and the Gigabyte P55A-UD4. Assuming you need the extra features of the UD4 of course. If you don't actually need an expensive board, the P55A-UD3 will do fine.
i agree on the psu being a bad choice... either go for antec or corsair or thermaltake toughpower.... ive had an 1200 watt toughpower for 2 years now and its done me fine.. and im running core i7 with 6gb ddr3 and 2x hd4870 x2's... plus a watercooling unit and all essential components... pulls less than 600w on a full load..
The toughpowers are OK as they use the same CWT internals that high-end Corsair units use. Some of Antec's PSUs are very good and others are bad, so it's always worth thoroughly researching an Antec unit before you buy. Generally it's safer to stick with other brands, though that said, Corsair have produced their first bad unit with the new CX series, so no brand is immune to producing lemon power supplies :S
Someone else running HD4870X2 Quad crossfire? Makes a change. I don't believe the 600W figure though, you obviously aren't loading all 4 GPUs. With an i7 you'll be drawing at least 750W from the mains under proper load (650W from the PSU), typically more like 850/750.