An Antec Earthwatts 500 would be my choice. Mine has been running for almost a year with no problem. Their warranty is also nice.
This is a good choice PSU for the OP's setup. 500W should be enough for his system, and the EA-500 has two PCI-E power inputs. It is also Antec's top rated power supply on NewEgg. I know OP has stated that he doesn't think his local retailer carries Antec, but it might be nice to check anyway.
Unfortunately, none of those are what I would call really good brands. I prefer Corsair and some Antecs.
I'd recommend a 550 watt Corsair if you could get one.
I don't really know about the others but coolermaster makes excellent power supplies. Corsair and Coolermaster are both top contenders. I'd never put one over the others except for the occasonal price difference between them. This subject is completely entitled though so i guess its based on personal expirience. I've just had an excellent expirience with both corsiar and coolermaster.
The general rule of thumb is a high quality 500 to 550 watt power supply with sufficient current (amps) on the 12 volt rail(s) can easily power a system with any single video card made. A high quality 700 to 750 watt power supply with sufficient current (amps) on the 12 volt rail(s) can power a system with two video cards operating in dual mode. There are a few exceptions like the new ATI Radeon HD 5XXX series cards which use less power due to their energy efficiency.
Corsair, PC Power & Cooling, and Seasonic are some of the brands that have a reputation for high quality power supplies that consistently earn high marks in technical reviews. They are reliable, stable, and come with a 5 year warranty. Lately we've been seeing a few other brands offering some high quality units.