If you want a 750 that's fine, if you want corsair, that's fine hell get a 850 if you want. Its all up to you. I wouldn't and that's my opinion, its right for me, maybe not for you.
PSUs are finicky, people do not understand how important a good and efficient psu is, they cheap out or get overpowered ones because of epeen.
There is a article of psu's
here and
here you can read, and I would advise everyone to read those 2 articles, I know wiki can be misleading but there is a great deal of correct info there.
Before you buy whichever you want look at Johnnyguru.com he does the best reviews in my opinion.
I read a review on the new Corsair RMs and they don't look bad, I wouldn't buy one but again, thats my preference.
No you don't need to future proof your psu, good manufacturers of motherboards and video cards are LOWERING consumption as they advance so there is no future proofing needed on more wattage unless maybe one day you plan on using Sli or xfire which I have never seen a use over a single card for normal people without epeen issues. There are psu calculators all over the web, google it and those will give you an idea of how much you need, read the articles first.
The psu is the most important thing in your pc, understand it and never cheap out and that doesn't mean cost wise either. Read the articles and you'll see why.