Hi I'm looking to get a Gigabyte 660GTX and my PSU is Topower 650W it has 2 +12V rails each 20A, now do I need to get something better like Seasonic or is this one ok?
The +12V drops to 11.6-7 in Crysis with the 9800GTX (using software monitor program)...
Your PSU should be able to run the GTX660 without a hitch, however, I wouldn't trust how long it will be able to run without damaging any of your components. I HIGHLY recommend swapping it out for something of higher quality. The Corsair CX430V2 PSU should suffice
A good quality such as that 620W PSU is likely to be electrically sufficient but probably won't have the required power connectors. You can use molex-PCIe adapters or 8-pin y-splitters to get more PCIe connectors.