old school orion XTR 475 is 75x4 @4 ohm (rated @ 12 volts!!!!!!!!!) 2 ohm stable, you can get for around 150 but you may have to search
also it has a crossover built in, mine is set up to run mids and highs off of channels 1&2 and subs on 3&4... also no matter how hard i pound it, it never gets hot