sorry. bad day. still friends?
as far over driving, your not gonna do that with one speaker hooked up to each channel of a head unit. (unless you seriously mismatch the powerhandling.) if your running, more than one driver off each channel, in series or parrallel, then under powering could be an issue, but you wont notice it in the sound quality, until the amp or speaker fries.
Now, you said your adding amps and subs, and that "maybe then you wont care because you'll be using the cross over anyway". i'm not sure i understand how your expecting this to fix your problem. by 2way amp, i'm assuming you mean 2 channel. this being the case, it sounds like your planning on running only the subs off your amp. you'll end up having to use the crossovers on the amp, not the deck, other wise youd be using the crossovers on the rear speakers as well. (maybe i missed somthing, but it looked to me like that deck only has front / rear crossovers, no seperate sub output.) which you dont want. If your still gonna be running the door speakers off the HU, (which is what it sounds like to me.) i would recommend, before installing the amp/subs , disconnect your front speakers and just play around with the settings for the back. make sure the rear crossovers are off. also, what is the power handling rating for those rear speakers. are they thee same model as in the front? your head unit is putting out 4 X 50W peak. if the rear speakers are different than the fron, it could be possible that the rears just cant handle as much power as the front.
if none of that helps, try switching the wiring for the front and rear. (hook your front speakers to the rear channel, rear speakers to the front channel) if the front still sound good playing off the rear channel, and the rears still sound like ass playing off the front channel, then it probally the speaker..... if the rears sound good off the front channel, and front speakers now sound shitty off the rear channel , then its either crossover or other setting on the HU, or possibly (hopfully not...) somthin wrong with that channel on the HU.
give it a go and let us know what happens... i promise i'll play nicely.[thumb]