Yes, I used speaker level input into a 2/3/4 channel Kenwood amp.
CH 1 to left 6x9 w/ high pass filter (like a crossover built into the amp),
CH 2 to right 6x9 w/ high pass,
CH 3+4 (bridged) to advent 10" sub in bandpass box.
Front speakers fed from the radio (I reccomend bass blockers for the puny 4x6 speakers, my Polk 4x6s still complain about bass)