I may be able to get some Def Tech BP 8B tower speakers for super cheap, I can't find anywhere if these have the subs built in or not. How good are these, I would imagine they would walk all over my current Polk Audio R30s, but if I got those, I would want to upgrade the rest of my speakers to match, at least the center channel. Can anyone give me some opinions on these? If I get them, it will probably be this evening, so I need to make a decision quick.