What amp would be a good upgrade from an Orion 8004? I have them powering a set of Mtx txc6.1's up front and Rainbow Sl165's in the rear. The amp seems not to have enough power to get the Mtx really going. They sound good but I can tell that they need more power or cleaner power. The rainbows are just fine with the amount of power they are getting. The Mtx's are rated at 150w rms. What would be a great amp to power these speakers with that would be a definite step above the 8004? Price wise I am looking to spend around $600 for the amp (authorized dealer prefered).