For question 2, I do the same thing with an active crossover.

I have 2 stereos, the crossover, a 4 channel amp, 4 main speakers and a 15 inch sub.
The tape car stereo (to be replace with the empeg) goes into the line input on the combined MD/CD player.. This feeds the crossover with the bass going into the rear channels on the amp (bridged to produce about 120 watts rms) and the treble going into the front channels (running the 4 speakers in a 2 ohm configuration at about 72 watts a channel rms).. I loose front rear fade by running the main speakers at 2 ohms, but I save myself an Amp.. =)

Obviously in your case filtering in the empeg will save you the cost of a crossover, but this is a way to achive it...
You are right to worry about your front speakers.. My friend has blown 4 sets of front speakers by not crossing them over properly..