Amp wiring

I own a Sony CDX-L410X In-Dash CD-Receiver (45W x 4).  I want to buy an amplifier and a subwoofer.

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.  Therefore, I don’t know if it is capable of providing signal to a 4 channel amp (Sony XM-460GTX) for my 4 speakers.  

First, Do I need 2 pre-amp outputs to power a 4 channel amp?

Second, if I do need 2 pre-amp outputs for a 4 channel amp, how can I wire the system to power 4 speakers with only 1 pair of pre-amp outputs and an amp?  Can I combine speaker level inputs on an amp with pre-amp inputs?

Finally, How can I wire the system so that I can power 4 speakers and one subwoofer using one amp and my present receiver (1 pair of pre-amp outputs)? Is it possible?  If not, what else do I need?

You actually have a couple of different options. 1st and maybe easiest is to get rca splitters to use a 4ch amp or you could run the small speakers with the hu and a sub with an amp. However most amplifiers will not allow use of both rca's and speaker level inputs.There are also some amplifiers that are 1,2,or 3 channel compatible. It is possible to get good results to with your hu having only one set of out puts. If you have anymore q's put up another post.

Thanks for your reply. what i really want to do is to power my 4 speakers now using a 4 channel amp and afterwards i want to add the subwoofer.  my question is: what is the best way of doing this? does it seem logical to you to buy a 4 channel amp with speaker level inputs, connect those and then connect a mono amp for the subwoofer using the RCA output? or is there a way to do it using just one amp?

Pioneer GM-X574-50Wx4 (4 ohms),65Wx4 (2 ohms), 130Wx2 Bridged (4 ohms), Lanzar makes 2 or 3 really good 4ch amps , and so does JBL. of the three I found I could get the lanzar the cheapest,Pioneer second and JBL was the most expensive of the three. But one thing I would say is stay away from "value" priced amplifiers such as Legacy, profile, and etc. Most of the time they are not worth even the small price you pay for them.