12 inch alpine subs? Any Ideas?

I have a dodge neon and just replaced the mid speakers in the front of the car. I took the tweeters out as well because the new speakers I bought have tweeters on top of them. Anyways, the tweeter hook ups are free so I want to add speakers maybe to the passanger side (down by the feet)...by rewiring obviously. Also, my friend has extra subs he just bought, should I take them and attempt to put them into the dodge neon? I don't think they'll fit. Anyways, do yall have any ideas what else i can do with the opened tweeter spots (i hate tweeters and want something better hooked up)? Any other tricky ideas with adding speakers would be cool! thanks guyziesss! :)