MTX is the only brand I have had experience with, I usually build my own and match other components (I like Fosgate speakers). The MTX powered Thunder forms are kind of nice, it's possible to build a better setup, but it isn't as easy. MTX used to build non-powered thunder forms for those who wish to use another brand of amp. If you are going to bypass the factory amp, run a wire from the head unit to the box and don't use the stock wiring.