With psu's you get what you pay for and £47 for a 650w psu is not a lot of money which would suggest that it's a budget unit built down to a price using cheap internals. I just can't see any other way that they would be able to put them out at that price. The thing is that we know very little about Cougar psu's and the STX series are relatively new and have no reviews at all. About all I can find out is that the oem is HEC and it has a single 12v rail of 624w. HEC are a low-mid end oem and are usually hit or miss as to the quality of the psu's. Cougar psu's in particular have not done very well in past reviews and the STX series appears on paper to be a very poor psu. For a psu that has just been released to scrape through with a basic 80+ rating (doesn't even qualify for bronze) is extremely poor.
The PSU is argueably the single most important component in a pc and is not the place to save money. Overall they are probably the best value component in the pc. A good quality psu is not really expensive seeing that you can get top quality, gold rated, fully modular units such as the EVGA Supernova G2 650w, Superflower Leadex Gold 650w and Corsair CM650x for £95-100 and the 750w varients for not much more. With the choice of top quality psu's available today for a reasonable outlay (much better value than a i5 for over £220) there is little excuse to put anything in a pc that scores less than 9/10 in reviews and is not at lease gold rated. This is a invaluable resource for information on psu's including the oem, strength of 12v rails plus links to revies (Jonnyguru is probably the best).
Back to your original question, as long as you are not overclocking I doubt that you will pull any more than 300w at the wall, most likely less so you
should be ok with the Cougar until you replace it. I certainly wouldn't have and I doubt that anybody else on here who knows what they are talking about would have recommended a Cougar psu to you in the firts place though. The old saying of buy cheap, buy twice is very true with psu's.
While the Superflower you have selected to replace it with is a fine psu they have got it out at that price by having fixed cables. To make cable management easier might I suggest a fully modular psu so that you only have to use the cables that you actually need. These are top quality units and are well worthy of consideration:-
My basket at Overclockers UK:
The XFX XTR series are Seasonic built units with a single 12v rail. The 650w version has a 648w 12v rail. It has a 5 year warranty.
XFX XTR 650w review.
The EVGA Supernova G2 series are built by Superflower and are basically a Leadex Gold with a different fan, no tacky leds and a longer warranty. Same as the Leadex Gold units they are all single 12v rail designs with the 650w able to deliver the whole of it's output on the 12v rail. It has a 7 year warranty. These are amongst the best units available today.
EVGA Supernova G2 650w review.
