Unfortunately it isn't as easy buying a similar sized woofer and dropping it in place of the old one. Usually a cabinet is built with the mechanical and electrical behavior (called the Thiele/Small parameters) of a particular woofer in mind. You want to do this in reverse.
You will also run into problems with the crossover between the old woofer and the tweeter. Unless its identical to the old woofer, a new woofer will probably not work in that range as the old one did.
And if you also replace the tweeter you will run into the same kind of problems with the existing crossover. You are essentially building a whole new speaker.
If you speak on the phone to people at Parts Express, they might have some idea of what woofer they sell that could work in your 201 cabinets. But it is also possible that they don't have anything suitable. Considering that these speakers were free, I think you've got your money's worth from them
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