A bit of both...

Got an old crappy car amp, and used the SMPS from it to power a fairly decent class D tripath module. Pics in this thread:
http://forums.overclockers.co.uk/showthread.php?t=17829129
The sound is good even tho I've only tested it briefly in the house with a small SLA battery. The module I've used is pretty much identical to the 41hz.com AMP9 kit and has no high level in...
The plan is:
Pre-amp from headunit > active crossover > cat5 > pre-amp in on amp 9
So pre-amped basically, no high level outs being used.
Almost, it's a 4 channel module, so channels 3 & 4 are for 2 subs, and channels 1 & 2 are L & R up front.
As for the crossover, I'm waiting on some TL072 opamps, once these arrive I'm going for this circuit
http://sound.westhost.com/project09.htm with a crossover point of 112Hz.
I want something compact with lots of connections, hence cat5... I could go with molex tho, I guess I'd need 2 x 4 pin connectors for 4 channels, which I may just be able to squeeze in...
FWIW, This amp will only do around 50Wrms with 0.1%THD, but this should be plenty for me really... I'm using stranded mains cable rated for 20A as speaker wire, and it works for me...