I'm thinking of buying a 600w but is that enough, or (as someone on this forum told me) is 550w enough. Or are neither enough? And if you could can you recommend me some, you think are good enough to power my build.
You are already well into the safe zone, that system with a 7850 wont be pulling more than about 350 W from the wall. A decent 500 W PSU can run any single graphics card system, so 550 W is plenty for you.
Any of the three Gothams finest suggested would do just fine for your system.
I'd like to be on the safe side, could you (or anyone else) recommend a 600w/650w psu please. Thanks in advance to anyone that replies
Unless you plan on running two of those cards a 500w psu will run a single 7850. If you want plenty of headroom then look at the XFX 550w psu. It's manufactured by Seasonic, and has 44 amps on a single rail. You can find it for on the cheap @ Dabs.