Dane,
For the volume control, look in manual at the "punch through" volume... that way volume and mute work on any source that's selected...

Raider,
For the crossovers... The absolute best thing would be to have the manuals for your speakers and look at a response graph or what they suggest as the lowest frequency the speakers will produce and go with the crossover frequency that's the higher one... (like if they'll do down to 50hz go with 60 instead of 40).... actually a quick search on google reveals that the fronts will go to 34hz.. so you could try running them "Large" or a crossover setting of 40.....

The next best thing would be to start at around 100 or so and work your way down till they sound the way you want them too...