I have an OK setup at the moment, but I can't help feeling that my sub is letting the side down. Its the only speaker left from my old prologic setup, and I got it from a friend for almost no money. Its a Yamaha YST-SW60 active sub. Would I get a much better sound from a reasonably priced new sub? I don't have a lot to spend on a fantastic sub - maybe £200-£300.