i have a 7 speaker system in my ride right now.. and im getting my parts list together.

this is the sub i will be replacing my stock sub with. air space is not an option, since im not going to build a new box, its out of the question.. so here's my speaker specs.

i need 1 amp, 1 channel, dedicated to that sub. looking for something decent. dependable.. yet not the most expensive amp on the market. any suggestions? SIZE IS IMPORTANT it will be mounted under the passenger seat.