I've dones the searches and have gotten some spotty info about this. My questions are:

Does an aftermarket H/U hook into the RF amp via pre-amp or speaker level outputs? Is an adapter needed?

If speaker level, is there a limit on how high-level the speaker outputs should be? The H/U's I'm considering are the Clarion ADB340MP, the Kenwood DPX-MP4070, and the JVC KW-XC77. These are all double DIN, CD/cassette combos with AUX input. Other recommendations with those features would be welcomed.

Thanks in advance,
Joey.

do some more searching in this section and all of your questions will be answered.

well from my understanding all the speaker wires from the Rockford HU run to the factory 300 watt (2ohm) amp via harness and output via harness as well

i want to overide the factory inputs for factory amp for the Front speakers and them run thru another amp i will install my self for the front speakers and then re wire the the rear speaker inputs from the HU into the amp then rewire the outputs to work in 2 channels instead of the factory 4 ... and buy dropping to 4ohms i figure the ampage be about 150-200 watts instead of the 300 watt 2ohms ... thus giving me 75-100 watts for rear speakers output and about 50 watts from the 2channel 100 watt lil amp i will install in the under the passenger front set

IS it possible to make this work?