After all the farce with the exploding Type R 580w versions I am surprised that is still going. I wouldn't let it anywhere near a pc. It has a very weak 12v rail of only 336w and considering how old it must be probably wouldn't even manage that much. If you use it and it fails then it will take out other components with it which a great many of us discovered when our 580w versions blew up. With only 336w it doesn't have enough power anyway. The GTX480 alone is a power hungry card and the Q6600 pulls a lot of power once overclocked as well. Do yourself a big favour and replace it with a quality 550w-650w psu. Take a look at these:-
The XFX XT series are designed by Seasonic but actually outsourced to a Chinese company for building to keep the price down. It doesn't make them a bad unit (I wouldn't suggest them if they were) although there are some cheap capacitors in them, it just means that they are nothing special but do get the job done. It is a single 12v rail design with 576w on the 12v rail.
The EVGA GS550w is a fully modular Gold rated Seasonic built unit with a single 12v rail of 540w and a 5 year warranty.
The Superflower Leadex Gold 550w is a fully modular unit gold rated unit with a single 12v rail of 550w and a 5 year warranty.
The Superflower Platinum King 550w is non-modular and is Platinum rated, has a single 12v rail of 546w and a 5 year warranty.
The Superflower Golden Green HX 650w is a non-modular Gold rated unit with a single 12v rail of 646w and a 5 year warranty.
The Antec Truepower Classic is a gold rated Seasonic built unit with dual 12v rails with 648w split across them and a 5 year warranty.
The EVGA GQ 650w is a Gold rated, semi-modular FSP built unit with a single 12v rail of 650w and a 5 year warranty.
I included the Superflower Golden Green HX750w because it is so reasonably priced. It is a gold rated semi modular unit with a single 12v rail of 744w and has a 5 year warranty.
Thank you very much for putting together a very detailed response. I'll take a look at those you have listed and take it from there I think. As you can tell I've been out the loop for nearly 10 years and now got a little bit more free time and money will be looking into upgrading everything within the next 6 months. But just wanted to get up and running again. Things have definitely moved on abit in the last 10 years!!
Still have one of the 580W versions in my spare PC... Still alive and well... Possibly a ticking time bomb, but you have to live on the edge sometimes...
On a serious note, pastymunchers post is excellent, and I don't have anything additional to add really. Other than the fact that the XFX XT will be fine, and I wouldn't bother spending circa £80~ on a PSU for that PC. Its to give some older gear a lease of life rather than to go in a brand new build after all.
OP, if this is to go into a new build 6 months down the line then ignore the XFX XT 600w. I only put it in there as a budget option for the spec you posted as it didn't seem wise to spend £70+ on such a old pc. For a new build though buy something decent now as it will last a long time. The two semi modular psu's in my list, EVGA GQ 650w and Superflower Golden Green HX750w are probably the best value for money due to their higher capacity for similar money as the 550w units.
Thanks very much for everyones ones advice. Long term the plan is upgrade everything at some point. I'm always one for trying to future proof as much as possible and if that's means I need to spend a little more on a power supply then I will.