If you want some thumping, I would start with the $600 range 12" ported subs. The subs I would look at are the
Hsu VTF2 mk4,
Rythmik FV12r, and
Outlaw LFM-1 Plus. They are a great combination of sound quality, output, and extension. Below that range subs start to make compromises that you really don't have to have golden ears to hear.
As for the JBL's being bleh, they are probably fine speakers, they just don't look like they are doing anything special. I have listened to them at Fry's, but I won't form an opinion on them from that experience since they were probably poorly setup and in a noisy environment. The EMPtek speakers cost about the same and I think they might be a bit better.
You might think about skipping tower speakers and going for bookshelf speakers instead. The chief advantage of tower speakers over bookshelf is their deeper bass extension, but since you are going to be using a subwoofer, you won't be using their extra extension. If you are interested in bass, it would make more sense to put that extra money to a better subwoofer. Some bookshelf speakers you might look at are the
HTD Level Threes,
Hsu HB-1s, and the
Ascend CBM170s. You would want to pair those up with their respective center speakers.
