Room size

You read so many loudspeaker and subwoofer specifications and how they're rated for small, small to medium, medium to large, & large rooms. Would someone finally define for me what these sizes are dimensionally? My listening room is 23' x 13' x 8' high with two exits to other areas (uncloseable openings). Is this a small or medium size room? It's on a first floor slab, no basement (oversized family room). I am using a pr of B&W DM601 S3's, an ASW300 Subwoofer, and two B&W M-1 satellite speakers powered by a Marantz A/V receiver at 90 watts RMS/channel x 7. I got to tell you the system rocks !! Yet these speakers and sub are rated for "smaller" rooms. This sub is considered small and mediocre in power but I've got to tell you, it has one helluva a punch. You can feel it in your bones!! Please someone clear this up. Many thanks.
In THX parlance, a large room is defined as anything larger than 4500 cubic ft. I think the parameter for small is anything smaller than 3500 cubic ft.
I should add that if the room is not enclosed, you need to add in all of the open cavaties as well. The basic cubic volume of your room is less than 2400 cubic ft, so it rates as a small room. The additional openings suck up some power, but I doubt you would notice it in your listening area.
Basically, your space is a typical small/medium domestic space, regarding the main listing/viewing area. However, as Jimburger mentioned, the adjoining open areas need to be considered as the ovearall space. These spaces act somewhat as a bass trap that sucks up more of the bass energy, all though not quite the same. The kicker here is that if your subwoofer is close to the wall boundaries in a given space, it reinforces the bass output somewhat, maximizing the output for frequencies that have quarter wavelengths greater than the distance between the woofer/port and the boundaries! Basically, making your sub more powerful sounding, with tradeoffs. If you have a large space, and only a modest single subwoofer, this is often the best way to get closer to proper bass output for your system. Of course, that also means reinforcing the bass modes in your room, which needs to be delt with really. So there's trade-offss.
The ideal way to do it, is to have the proper amount of woofers and power in your system, have the woofers properly placed for more accurate/flat response, and get even more efficiency and impact from your system. Todays digital subs however, and basic analog as well, have parametric EQ's on board, which allows you to dial out the bass mode peaks from your listening possition(s?)! This greatly affects accuracy, and is a very valuable addition these days...very effective! Another route is using an onboard eq from some of these new pre/pro's and outboard processors, like the Audyssey stuff in the Denon.
Still, everything depends on setup, acoustics and calibration. If you like what you have, I wouldn't sweat it.
My thanks to all of you who replied. It's all excellent info. I'm relieved to see that the industry defines room sizes to be small under 3500 FT3. That's what I've been trying to find out for some time now. Yes, the openings in the room can suck up some of the bass but it really is not that noticeable. It comes down mostly to the recorded quality of the music being played. From CD to CD and even cut to cut on the same CD, it's astounding to hear the differences in bass response. Some pound with bass and I have to back off the sub volume and bypass filter. Yet on other CD's (generally the earlier the recording, the less bass), you have to crank it up. Many of the earlier Beatles CD's for example sound tinny and thin yet when you crank up the White Album, it rocks. A lot has to also do with ample power from the amp to drive the loudspeakers as Flrnlamb described.

I love this forum. I am learning a lot from those of you with more years in this than I. Thanks again. I'll be back with more questions.

"From CD to CD and even cut to cut on the same CD, it's astounding to hear the differences in bass response. Some pound with bass and I have to back off the sub volume and bypass filter. Yet on other CD's (generally the earlier the recording, the less bass), you have to crank it up." (PDN)

This is a VERY COMMON PROBLEM with the majority of peoples system's out there really. What happens is that the balance of things is very off most often in a system. And the problems lie in the bass response peaks and dips, the level matching, and even the phase between sub and speakers and such! Basically, people have things all out of wack, and ill-set up.
A major problem usually has to do with speakers and subs (and correspondingly, the seating possitions) not being properly setup for flattest and most even response from speakers to seats. Because there's often large peaks for instance in the bass response from most people's systems, what happens is that every time the problem frequencies are covered by the source material, the added boost (or distortion) at those frequencies makes the system sound boomy and MUCH LOUDER at those problems spots...thus giving the impression of the system being too loud! Then, you turn things down. Then, when passages get quiter, you go back up on the volume...then back down again...then back up again!!! This is NOT GOOD! The same problems occur with dips, just the opposite, but same effect really. And, there's more. But the basic issue is lack of proper setup, bad response at the seating possitions, lack of proper calibration, etc, etc. Really, there's a lot to be covered in a properly set up system. Most miss it.