The RM850 is a good unit (unlike its little brother the RM650), but it uses some crap quality Ltec capacitors. The Super Flower-based EVGA units are the top picks here.
TNattyThe RM650 is missing two wires in the ATX spec, and the RM850 has better build quality. Both pale in comparison to the EVGA G2 series. You can check out the jonnyguru reviews to learn more.