The Corsair CMPSU-600CXV2UK is decent, but not something I would buy.
Pros: Dedicated single +12v rail, sleeved cables, long cables, plethora of interface connections
Cons: Not modular, +12v rail max output is 40A, no certification (80+ or better),
I'd be quite concerned about the reliability of a company that puts out wrong/misleading information about their products. Check out their spec sheet on their builder series PSUs here
If you were to simply 'go with' the numbers they have on this sheet, you think that the 500 is better than the 600, but you'd be wrong. The 500 doesn't have a max load of 56A. But, apparently, they'd have you believe that just because you're reading English, the PSU can handle an extra 12A.
In my opinion the GS600 > the CX600