Amp Wiring w/ one pair of preamp outputs

I have a pair of factory speakers in the front of my car (don’t know their watt output) and a pair of Sony 250W oval speakers in the back.  I also have a pair of 80W tweeters in front.  I want to add a subwoofer in the near future too.  I want the most I can get out of my system.  My concern however is that my receiver only has 1 pair of pre-amp outputs. 

First, is one pair of pre-amp outputs capable of providing signal to use all channels in a 4 channel amp (ie. Sony XM-460GTX)?.  If indeed it can, can you please tell me how?  If not, what should I do?

Second, how can I wire the system to power 4 speakers using an amp, one pair of pre-amp outputs, and speaker level inputs?

Second, if I buy a subwoofer later on, is there any way that I can amplify my entire system (4 speakers & 1 subwoofer) with one amp?  If not, what else will I need and how can I wire it with one pair of pre-amp outputs and speaker level inputs on the amp?

Thank you for helping me out.