Main connector is for the motherboard... newer motherboards with PCI express video cards have 24-pins
older ones have 20-pins. Most 24 pin power supplies come with an adapter to connect to older boards.
Depending on your case manufacturer there can be issues with width of some brands of PSU-- you should not "rush purchase" this. Measure the one you have now. Height or depth is usually not a problem... but this is a Sony (?) I have no experience working on Vaio products.
500-600W should cover most anything you want.
You almost certainly have an ATX power-supply --AT's are quite rare these days. ATX 2 is a brand-new standard-- you won't need it-- but if you have it --it should be compatible with your board.
Modular cabling is not critical.

All the brands you mentioned are quite good.
STAY AWAY from "bargain basement" power-supplies. When you are putting the most demand on your PC is not when you want it to shut-down for lack of power.

Research is a necessity ...as I said you want to be sure it will fit. 90% of them will-- but if it doesn't... it's no good to you.

cheers for that ih8bills!

that's why we're here, eh?

sorry I just got my internet up and running again. Thanks a lot guys apritiate it.

Well I just went to Circuit City and got a Antec 650w for $99 but it just doesn't fit on my case. If you guys know of any PSU that will fit in a SONY VAIO VGC-RA930G please let me know.

Is the Antec and ATX power supply? What is stopping it from fitting?

Hi Platinum.

The sony cases are designed to have specifc power supply's. I'd suggest talking to circuit city and asking them to have a quick look to see what kind of PSU your case support.