Corsair CMPSU-400cxuk http://www.scan.co.uk/Products/400W-Corsair-Power-Serie...
As long as you are NOT quoting specs from a Dell system, then any ATX power supply should be compatible. This psu has a 6 pin PCI-E connector for your video card in case you have the higher power version of the 9600 GT. The psu also should have enough other cables for your system as well. It has plenty of power to run what you have at a pretty good price.
Yeah, it will really work fine, and for years.
Remember, there are cheapo psu boxes out there that say 600 watts.
Look at the amps on the 12v rail. Your system will not use anywhere near that much power. If you had a different motherboard (that supported SLI), you could use a molex --> PCI-E 6 pin adapter for a second videocard and it would still have enough power. For what you have this is a high quality psu that meets you needs at a good price. If you want to spend more money, go to jonnyguru.com and look at better boxes. Brand for power supplies turns out to be an important factor.
Corsair CMPSU-400cx has 30 amps on the 12 volt rail. That will be plenty. But if you really want to spend more money, get a 450VX. Of course, it has only 3 amps more on the 12 volt rail, but it is a 450 watt PSU.