I'm afraid the physics is against you when it comes to speakers. Having designed them for many years I know the pain of trying to get a quart out of a pint pot. If you want those bass notes you have to move a lot of air. This means either very large drivers or small ones that move in and out a great deal. The latter are difficult to design and make which is why we still have to use the large ones if we want to make a lot of noise. In any case, the loading on the rear of the driver has to match the amount of air being shifted if you want a clean and extended response. Yamaha did the right thing in using those wooden cabinets for the 9000. Wood (or its equivalent such as MDF) is a lot deader than plastic and doesn't contribute nearly as many resonances to the sound. And they're also the right size and shape. If you want quality you have to pay for it, physically as well as from a monetary viewpoint. This is why my 740 doesn't sound nearly as good as the 9000. Just wish I had the wherewithal to buy one.

Bryan