I am currently looking into buying a new head unit for my car. The only thing is is it doesn't have a subwoofer preout, it only has a 2 channel preout. Would it be possible to still use the 2 channel preout to connect to my sub amp?  

Absolutely!  Even if it only had a single pre-out it doesn't have to be a dedicated subwoofer pre-out to be able to connect it to a subwoofer amplifier.  Dedicated subwoofer preouts have built in low-pass crossovers that cut out the high frequencies right in the head unit, thats the only difference.  Since almost every amplifier made today has both highpass and lowpass crossovers built into them it makes no problems taking a regular preout from a head unit and connecting to an amplifier that's powering a subwoofer.  Just remember to turn on your amps lowpass crossover and set it to a frequency that blends well with the rest of the system.  The easiest way to do that by ear is to turn it on with the adjustment on the crossover all the way up and slowly back it off until the bass from the subs becomes hard to pinpoint to the rear of you.  Sounds kinda funny but the intentions for a great sounding system is that the bass from the subs comes from in front of you, or at least that you cannot tell where its coming from.  When you go to a concert for example you don't stand with your back to the stage do you?  The music, even in a recording studio, is recorded with the element that it's being played directly in front of you and anything in the reproduction by the speakers, including subwoofers, should sound as close to that as possible.  Unless you're just using them for SPL then leave it all the way up and let the subs reproduce all they can on the lowpass and it'll gain you a little more SPL.  It all just depends on your tastes at this point in your life.  I used to be an SPL junky until I started to see and listen to some really nice SQ vehicles and it turned me right around.  Good luck and Enjoy!!!  

Thanks a bunch, I'm not really in it for the SPL, I just want it so it sounds good inside the car. Once again thanks for the advice, can never learn enough ya know.