02 silver si

A little over a month ago I put in my first head unit and I had upgraded to Infinity Reference speekers a while before I had done the head unit. Well I am liking the sound a lot but I would just like to add that little bit extra to make my EP sound great. I know what I need is a sub. I am not a guy who likes to be heard for a 1/2 mile I just like like hard rock, heavy metal, and some rap and I love bass but not to any extreme. On my home stereo I have the base up to about 2/3 of the way on the sub.

From searching it seems like most guys like with their stock setup, but not with a aftermarket setup. What I am wondering what setup for me. To get a baselink or to try and make a custom sub setup on the floor to fit over spare? I just dp not want to take up a lot of room in my EP and all I will need is a single sub.

Thanks for your help. Thought I would ask before I make a misstake that will cost my a lot of $.