Loudest deepest sub? I'm thinking four LAB subs and an I-Tech 8000. After labor and costs, you're looking at around $6000.
I do not think this is what you're looking for, and I don't think what you have will cut it. You will definitely need a good amount of (read: couple thousand) watts from a quality amplifier, and a quality sub. Even an RMX2450 would suffice for a budget rig, bridged into a pair of SRX718's or an SRX728. Even that's gonna run you about $1500 total.
Bottom line: there is no cheap way to get loud deep bass.