Two subs in a small room....

10x10 room will tend to amplify 55Hz (1125ft/s / 20) - not ideal since many speakers have port tuned to about 30Hz and get already hump on 60Hz. Bipolar speakers cancel this effect by directing sound in both directions (canceling). Similar effect can be perhaps achieved by using two subs facing opposite directions. AFAIK sound at low frequencies is not directional. Two subs are often used to reduce room effects (peaks and valleys) and not for the amount of bass or imaging.

If you are looking to enhance lower frequencies without much care of accuracy, then by all means get a sub. Tune it low, and you will be fine. Reduce the volume if needed. You can pace a sub almost anywhere, for any reason and get good results...IF you do not demand accuracy and perfect synergy with the speakers, do it. I would only purchase 1 sub, 10 inches min diameter. Later add an additional one IF your space increases.

Look for a passive sub. RA Labs (Roy Allison) made some good ones and they show up in the used market at very low prices. Essential they pull out the lows and create a great mid range.

BTW, as to placement:

The whole idea of 2 subs is to have each sub excite the room differently. This usually (not always) means asymmetrical or "random" placement. One key is to keep the subs close to the nearest wall (or walls, corners sometimes work well)so that there is less cancellation of the original bass wave from the sub with the reflection of that wave off the walls. These cancellations - and accompanying reinforcements - cause significant irregularity in bass response below 150-200hz from most speakers. Unless your room is large enough - speakers >15ft from the nearest wall - to behave like an anechoic chamber, you are unlikely to get the smooth response you see in that speaker's anechoic FR test. This is no reflection on the speaker, just an illustration that deep bass should be generated near the walls in "normal" listening rooms.

With due rerspect to Vandermeulen, with the exception of digital room corrected speakers, I have never seen accurate (as measured) bass response from a freestanding speaker that can approach that from a correctly implemented subwoofer systems.

And note: I have measured the bass response of my systems for years.

Marty

My desire is for a smoother, richer sound as opposed to "more" bottom, if that makes sense. I have one sub already and my bottom end is fine but keep hearing that two subs would give a better audio presentation. I've been thinking that the room I have my system in may be two small for two subs but maybe two "small" subs may do the trick.