Hi and welcome to the forums.
Your current psu is garbage that is only fit for the bin. It's a cheap and nasty unit that has nowhere near 750w on the 12v rail and you would be lucky if it even had half of that. Never, ever cheap out on the psu. A decent quality 550w psu would be more than enough for your pc so have a look at these:-
Non-modular (fixed cables)
My basket at Overclockers UK:
Total: £85.49
(includes shipping: £10.50)
A Platinum rated Superflower psu with a single 12v rail of 546w and a 5 year warranty.
Semi Modular (mix of fixed and removeable cables + Modular (removeable cables)
My basket at Overclockers UK:
The Corsair TX550M and TX650M (included as it's only a fiver extra) are gold rated semi modular units built by Great Wall for Corsair. The fixed cables are the 24 pin, 8 pin cpu power, a chain of molex and a chain of sata so probably cables that you would probably be using anyway. The 550w version has a single 540w 12v rail while the 650w version has a single 612w 12v rail. Both have a 7 year warranty and you can read a review of the 550w version
here.
The Bitfenix Whisper M 550w and 650w (again included as the price is close) are gold rated units built by CWT for Bitfenix and all have a 7 year warranty. All cables are removeable so cable management is much easier. The 550w version has the full 550w available across triple 12v rails and the 650w version has the full 650w available across quad 12v rails. Each rail provides power to a certain group of components so:- 12v1 Motherboard and peripherals, 12v2 CPU, 12v3 GPU 1, 12v4 GPU 2 (650w and above). These units have one downside and that is that they have a shroud over the 24 pin connector amking it stick up from the motherboard more than a standard cable. Not a problem if you have a case without a window but if you do have a window you may not be able to live with it. You can see it on page 2 of
this review of the 550w version.
The Superflower Leadex Gold is a gold rated fully modular psu from Superflower. It has a single 12v rail of the full 550w. It has a 5 year warranty and you can read a review
here. The downside is that they have bright white leds that cannot be turned off where the cables plug into the actual psu.
The Seasonic Focus Plus is a new series anly recently launched and have been getting excellent reviews. They are gold rated, fully modular and very compact at only 140mm long. It has a single 12v rail of 540w and has a 10 year warranty. You can read a review of it
here. If I was looking for a psu right now it would be from this series. Unfortunately it's out of stock on here at the moment but is well worth hunting down from another retailer.
As for your overheating problems I assume that the case that the psu came with is of equally poor quality and has poor airflow through it making it act as a hotbox and cooking your components. Add in a hot, power hungry cpu and it's a recipe for disaster. Sorry to be blunt but that's my honest opinion. What case is it and does it have any vacant fan positions?
