Ignore PSU tier lists, they all suck because they're inaccurate, biased, or out of date. Look at professional reviews only, don't trust some schmuck's opinion with too much time on their hand:

http://www.realhardtechx.com/index_archivos/PSUReviewDatabase.html

The original RM line made by Chicony was a good unit with an issue with its low fan mode. Corsair fixed these issues and rereleased the RM line. They did so again improving performance and changed the platform to one made by CWT. You most likely bought the good one made by CWT or at least the fixed Chicony version. Both units are fine, though the CWT is better.

http://www.orionpsudb.com/news/corsair-releases-new-improved-versions-of-rm750-rm850-made-by-cwt

(850w reviews, but performance is similar to 750w)

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=369

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=422

Johnnyguru's thoughts on the whole thing:

An awful lot of these people exist on Internet message boards, I'm finding, and they all seem to love hating on Corsair lately... the original RM850 still gets way too much hate from these people. One little design flaw so minor that it affected exactly zero consumers, and suddenly Corsair is the devil to some and now the RM series is crap not worth buying... Folks, if you're one of these people, here's my personal opinion on the entire Corsair lineup, as I've seen things: some units they make are world class. Others just get the job done. Exactly zero are pure crap. They're all decent.

If you want to know whether the unit you got is the CWT or chicony, look at the serial number on the unit. If it's s/n> 1341xxxxx then you have nothing to worry about.