Bangin is rioght , Double speaker cone size is +3db. Then, double power to all subs, thats 3 more db. If it was only about $, someone would have hit 200 by now. Its about science. The wall at 150 db took years to get by, the one at 180 even longer. 200 is virtually unreachable.
Also, ALOT of local people w/ 150 db cars were NOT measured on a good A weighted meter, so IMO, they dont count, Try it on a good RTA and see a low 140...that what they actually have anyway.