if you are looking for under $100, you can find like the new Sony Pentagon 5 sided Subs online for around $50, but Sony does not come super highly recomended by some on HAN. I have had no problems w. their HUs and think they have overall good quality. There is also the JL 12W0. This will run you more money but itll sound good and given the right rated rms power, won't be too overbearing on your system. There is also the Rockford Fosgate Punch HE. That also has good amount of bass for a decent price. In that range there are a lot of subs. Go out to BB, CC, and any other local audio shop and listen and see what you like best. These are three starting blocks to look from.