in that range, it looks like you'll be looking for audiobahn, jbl, kicker, or rf. If this is for an sq sub, you'll want something better though. I'm pretty sure its not, but thats just my disclaimer on recommending those amps.
sh!t not sure if its exactly in that price range but the Kicker KX600.1,JBL GTO 600.1,and MTX Thunder 6500D should be close to that price range and all work pretty good...of course thats buying off ebay
The KX600.1 is close, but a little higher. Of course, he should save a little more before buying the Audio...
Anyway, just do a search at eBay with "600" and various name brands. Try Orion, JBL, Kicker, Directed, Memphis, Viper, Alpine, PPI, etc. Just be sure the amp does the 600w at 2 ohms like you specified. Look to Hifonics if you want it really cheap, but a 600w amp rated by them probably won't do the true 600w. You'll have to go a little higher.
Power Acoustik "Gothic" 1200 Watts Max 2 Channel Amplifier 2 x 300 Watts RMS @ 2 OHM $160 shipped cardiscountstereos.com
If a sub is 4 Ohms DVC does that mean each set of voice coils are 4 ohms? Also, if thats true... can i get (2) 2 channel amps that are 300RMS in bridge mode and bridge a set of voice coils to one and the other set of voice coils to another?