Need help buying Subwoofer

At under $300, individuals like the BIC PL-200; at around $200, the BIC F12.

Go to the set of comments related to those subwoofers on how to get the best price.

I'm not sure what you mean by "mid sized" room -- because everyone's definition probably differs -- but one sub you should consider looking into is the OSD PS12. I just posted my review of it's little brother, the PS10, and found it to be surprisingly good. The PS10 was certainly worth the asking price, so I imagine the PS12 would also be.