I am going to upgrade my current sub and I have decided to go with an SVS sub. But there are so many options that I have no idea which one to get. My room is about 18x20 but it has a high vaulted ceiling and there is a large opening to the foyer at the front left. I have pretty much decided to go with a dual-sub setup. Is the big difference between the PCi and the PC-Plus? Another key question is are the tubes alot better than their boxes? Would a PB12-Plus/2 perform nearly as well as 2 PC-Plus subs? And what about getting the unpowered versions? It seems like it would be cheaper to get 2 CS Plus subs with an external amp. Sorry for all the questions but I am eager to make a decision and get my new sub(s).