subwoofer out

I just got a alpine deck installed in mar car, i dont know what model eactly it was but it was about 500 dollars , and it has a sub out.  They didnt wire this sub pre out to my subwoofer , so im just running the subwoofer on a set of the pre outs for the speakers, i was wondering if i rewired it so that the sub pre out was running the sub amp directly if it would give me more bass?

possibly...if you ran the rcas to the sub out instead of the rear out, you would have the ability to turn the bass up on the sub only not affecting the door speakers.  so it depends, but if you have a sub out...its always the best idea to run rcas to the sub out, thats what its there for.

Yes,use the sub out, that way you can use the internal crossover for the sub and internal crossover for the rest of your speakers. You will have way more control over the system and you could possibly achieve better sound quality/spl.