OUCH!

$500 American doesn't go too far with bass amps.
I myself use a Peavey Sessionbass head into a 2x15 cab (also Peavey). Soon I hope to invest in a Sunn 1200s head ($1,000 US) and another 2x15 cab, but I still have some saving to do... that's a bit above what you're looking for.

If I were you, I'd stay away from Peavey TNT and TKO amps, Fender solid state amps, as well as anything by Crate.

Look around a bit and see if you can find a Traynor head and hopefully cabinet. I had one when I was starting out, and today I wished that I hadn't traded it. They'll be heavy as hell, but they're tube amps, have excellant tone, are made in Canada, and are old enough to sell for cheap.