Choosing a build.

I agree with the above, but I'd rather get an HD 5850 instead of the 6850. It's more powerful, yet usually around the same price. Either would be fine though...

I'd also swap the HDD for a Samsung Spinpoint F3. The 500 GB is 30 pounds or the 1 TB is 39 pounds. These would be faster than that Western Digital drive.

As far as PSUs go, I'd eliminate Xigmatek, Coolermaster and OCZ from that list. They're not the best quality. Instead, add XFX and Silverstone to the list. Since you're looking to Crossfire (SLI and AMD is a horrible idea), you'll want at least a 650W unit.

Finally, I don't think that RAM's that good. Since it looks like you're wanting to overclock, I'd pick up some 1600 mhz CAS Latency 7 sticks, like these G.Skill Ripjaws for 55 pounds. At the very least, get 1600 mhz CAS Latency 9 sticks. They'll be a lot faster once you start overclocking.

The 6850 is newer, so it's still likely to get a lot of performance gains from new drivers. In addition, it scales slightly better than the GTX 460.

Finally, since you're doing an AMD build, nVidia isn't really an option. AMD doesn't natively support SLI, so the boards that do support it are often pricey, low quality and unreliable. Basically, if you choose AMD for your CPU, and want the future proofing that dual card solutions offer, you're handcuffed to ATI (which is AMD).

As for pricing, the 5850 is around $170 on Newegg and the 6850 is around $180, so that's my source. No idea on UK pricing, but that seems pretty fishy. Regardless, the 5850 is more powerful, so a higher cost is rational.

The only other UK sotre I can think of is ebuyer.com.

16x/16x doesn't make a difference. The performance loss is at most 3-4%, and only really has an impact if you're using the 5970. Don't bother paying the $50+ premium for a 16x/16x board over an 8x/8x one.

Newegg will not ship overseas, so you'd have to use an intermediary (i.e. you buy it from Newegg, Newegg ships somewhere in the US, the US receipient ships to you). You'd likely have to pay some kind of import/custom fee. I doubt you'd save anything in the long run.

I don't believe there'd be a technical difference in the parts, but I'm not sure. If there was a difference, the only part that I could see it effecting is the PSU.

Best is extremely relative. Once you've made the changes above (X3, ASRock board, good PSU), it's certainly a great build. Of course, once you start talking about putting the 5850/6850 in there, it's going to be more in the $700 range...

there should be only about $10 difference between a 460 (fine as a single card) and a 6850 (about equal to the 460 solo, and scales wonderfully in crossfire)

the main difference would be stepping down on the graphics card

It's prety decent. I'm not a huge fan of the Coolermaster PSUs, but it should do the job. I generally consider them to be a second tier product. If you've got the budget left, I'd try to grab a 650W Corsair, Antec or XFX (SeaSonic and Silverstone are likely out of budget).

550 shoudl be fine as it is. CoolerMaster is, however, a good brand, I'd stick with that 650 you have, which will leave plenty of room for a second 6850 later.

You only will need the Hyper 212+ If you plan to overclock.

I'm not saying Coolermaster makes really bad PSUs, I'm saying that they aren't the highest quality. You can live with them if you have to.

I don't think the 600W would be big enough. I'm also a little troubled by the lack of an 80+ Certification. I believe Corsair's CX (their "Builder's" series) are their low quality, budget line. Is there not a Corsair 650TX (or if you're feeling fancy, the HX)? Or Antec's Earthwatts 650W (EA650)?

If the choice between those two PSUs only, I'd lean towards the Coolermaster.

Is that including the Hyper 212? If it is, and you aren't overclocking, you can remove the Hyper to free up some budget.

Yes. I didn't see that you said you were going to OC eariler. I'd probably just keep the HSF in the purchase. Replacing it later is a pain in the ass.

yes, they do.

Thanks not really relevant to the build yet but wanted to check.