2 Head units in one system?

I'm wiring up 2 head units in an f-350, its a quick add on to a complete system so that the truck has a cd player for a road trip, now my plan is to run new speaker wires from the front outputs on the head unit and go to the front cross overs since the rear speakers dont work that great anyway, does anyone see a problem with this? i've got the head units wired up to a toggle switch that shuts off in the center position so that left the stereo is on, right the cd player is on, since only one has an antenna lead going to it, the memory on both units is supplied a constant 12v thru the center terminal on the switch, any thoughts or ideas?

J~

that was the main reason for posting, wondering what the effects of having power supplied to an out on an off deck, of course the one deck is pretty much a write off as i havent used it in awhile, the other deck is pretty old and would just give my brother a reason to change decks finally lol, the toggle works extremely well, the memory stores on both decks and with the switch i can select which one gets power which so far hasnt cause a problem with the speakers or the outputs of the decks, still working on getting sound out of the cheaper head unit as i think one of my grounds went wrong when i put the origanal deck back in the dash, i'll fill in anyone watchin tomorrow night as i'll be done by then, but i would like to hear any issues this setup might cause of a pro installer might know any.

J~

I installed the secondary head unit in the glove box, ran all my wiring tucked underneath the dash, ran the speaker wires from the head unit directly to the speaker crossovers, 16 gauge wire from the headunit down, toggle switched the power supply so its like a selector, all done in a couple hours, hooked up everything, checked all my wires and boom no sound out of the speakers, flip the switch other head unit works fine, flip it again secondary comes on, lights up, plays cd, no volume, anyone got any tips? is it possible to fry a power amp on a deck if the speakers arent connected when its powered up like the old stereos used to do?

J~

Use a switch for which HU the speakers should control. Or use a stereo mixer IC. But only if you can find one to handle the power, otherwise you'd have to use preouts and then amplify after the IC.