A little advice needed-

I'm just finishing up the install on my new audio equipment, just need some
advice on how to set the gain levels.

What I have right now is a Kenwood head unit sending front and rear preamp
signals into a 3 way active crossover. Front and rear from the crossover go
to a 4 channel amp to drive the main speakers, and the subwoofer output goes
to a mono subwoofer amp.

My question is, the crossover has it's own level control, as does the the
amp. Which should I adjust first for best sound? I have an idea on how to
set crossover points (adjust 'till it sounds right, right?)

Thanks in advance,
Mike O'Malley