Damn these threads are popular today. Ok, I've got chocolate at hand and I'm mostly repeating myself (or regurgitating CustomPC magazine) anyway, so... fight!
- Nice case.
- Nice CPU. If you don't care about overclocking, then there's no problem. The 2600 (non K) can only gain an extra 400Mhz or so due to its locked multiplier, but the 2600K can get as far as 5.1Ghz of the 5.4Ghz theoretical maximum (IIRC... it may have been 5.2 out of 5.6 maximum, but I'd have to dig out the right CPC magazine issue for that). If you're going to overclock, get the K version.
- Lots of people don't like MSI because of the number of features they cut, and the motherboard you picked out isn't one of their best. CPC basically have 2 recommendations in terms of value. The Asus Sabertooth P67 (with "thermal armour" technology) has the best ratings when playing games, but is not the best at overclocking (probably due to the unique thermal armour design it has) at £155. The MSI P67A-GD53 is the best overclocker (leaving aside the ASUS Maximus IV Extreme, which is just too expensive) at £109 from ebuyer.
- Nice graphics. As you mentioned, the GTX 570 is better, but the HD 6950 is still good and is more affordable. One thing though, please don't use "ATI" - they don't exist. I know overclockers used ATI too (which they're not supposed to), but AMD acquired ATI a couple years back and they're no longer using the ATI brand (starting from the HD6 series, it's just AMD).
- For the PSU, 850W might be a bit overkill unless you plan to go CrossFire at some point in the future. Then again, you can never get a PSU that's "too powerful", and not going near 90% load will extend the lifespan.
- Good selection of HDD. Certain WD Caviar Black HDDs (basically the newer ones, but they don't make it easy to tell which ones are which) do have better performance than the Samsung Spinpoint F3, but the F3 is cheaper so better value. Also, in RAID arrays, Spinpoint F3s are recommended over any WD drives (based of Toms Hardware) and, in a big enough array, can even beat some SSDs. Caviar Blue HDDs are roughly the same price as Samsung HDDs, but Samsung performs better.
- DVD drive... not much I can say. £20 is standard, and Pioneer are one of the more preferred brands with system designers.
- 8GB of RAM is overkill, and it's unlikely you'll even use up 4GB. Then again, times are changing and high-powered systems are starting to see the benefits of having 6GB of RAM.
Aside from the suggestions I made, there's not much to say. Oh right, useful lil fact. Since you're in London, you can find some very good deals in the saturday computer fairs (particularly the one in Tottenham Court Road). There's even a guy there I know who is often willing to undercut online prices if you're getting a lot of parts from him (or maybe it's just me, because I keep going to him when people ask me to build new computers for them).
EDIT: @meornot0, the 2600 CAN increase the multiplier, but not by much. A 2400 can be overclocked to around 3.9Ghz, so I imagine a 2600 can be overclocked a bit further. Fun fact about Sandy Bridge though: the base clock cannot be overclocked by more than 5Mhz (from 100Mhz) without crashing. Overclocking a Sandy Bridge CPU is almost entirely about the multiplier. Here's an entire
page about overclocking Sandy Bridge (and the limitations of the "locked multiplier").
EDIT2: I forgot to mention... regarding nVidia vs AMD... leaving the drivers aside, nVidia cards are better at rendering than AMD cards, and this translates to better performance in games with plenty of post-processing effects. There's a couple other things (regarding the differences in technology), but that'd be too complicated to explain (so I try not to remember it).