Newbie amp question

Can I run a pair of component speakers and a sub woofer if my head unit only has one set of preamp outputs?

The amp I'm getting has inputs for front and rear and I was wondering if the rear outputs will have power if I only use front signal inputs.

Yes you can do this. Most amplifiers are capable of deriving a signal off of only one set of inputs, check to see if yours is one of them. If it is not then you will need 2 rca y splitters like the Scosche afmmyc.  www.scosche.com

There is only one downside to using Y- adaptors.  You lose the ability to fade front to rear.  But that is it.