How to audition subwoofer?

Would any please tell me how to audition a good subwoofer w/o dragging my own subwoofer to the store? I have a Polk Audio PS350 (10" 150w w/ variable crossover 60-160Hz & frequency response from 25-180Hz). I went to the Good Guys to audition a $1200 Velodyne sub (sorry don't remember the model #). The rep closed all the doors of the sound room, put in the CD, and cranked up the volume of Parasound separate system. It sounded so boomy that I didn't find it any better than my current sub even though two salemen used the exact same lines, "Velodyne would blow your sub out of the water." I was thinking how? By shaking my room? My 12X13 room was already shaking with my current sub. I was hoping to hear the tight bass that I have heard from this websites and others similar. They told me to bring my sub in for side by side testing, but before I do so, I like to consult with Audiogon members, i.e. how do you audition a thousand-dollar subwoofer. What is the trick? My preference is 1:1 of movies:music. Do you prefer dual 12" for push and pull? Do you like the down firing? If I get a better sub, I was thinking of stacking them and use a Y splitting cable. Or should I just forget about upgrading to a better subwoofer by taking an easy route, i.e. getting another PSW350 to place each behind a main speaker to get better marginal affect. Any personal experience. Please shed lights. Thank you for reading.