im going to buy a new case, psu, and cpu heatsink. ive been more worried about the psu than anything else since ive never found a GOOD reliable one with almost no RMA reviews of it. I narrowed it down to corsair as the brand but i looked at the reviews and about 10 of em died within 3 months which is worrying me. from an experienced users view, is corsair good enough to live for like 10+ years or should i keep looking?
Corsair's a pretty reliable brand - one of the best in the market. Those 10 PSU deaths (from customer reviews I'm supposing) are a small fraction of what has been sold - it's impossible for all PSU or graphics cards or RAM to be fault free, that's why RMA exists.
The Corsair HX850W is a nice PSU, but considering you're only going to use another GTX 275 later, then the HX750W is perfect for your needs.