If you want a decent amp, you're looking at 1000 - 1200 rms in that price range, buying an amp new. You may find a decent used amp for ~$300. Its also going to depend on the DVC of the subs, I'm assuming they're DVC 4s and you can run them at a 1 ohm load. If they're DVC 2 ohm woofers, you're going to have to increase your budget pretty nicely.