I have the 600 and I can give you my impressions on that. Apparently the 500 is very similar with a slightly shallower bottom end and less power. Given your room size, power on the 500 is a non-issue. My room is a similar size to yours and I have a large opening by the staircase leading to the upper level.
I can describe my 600 as VERY powerful. I have it turned up very little and have LOTS of headroom. You will never have to worry about damaging it by over-driving it. I have tried to "kill it" by playing the truly torturous Plastikman:Closer CD at maximum volume and could not. But at the ridiculously loud levels and sub-20 Hz that this CD was pumping out I could definitely hear the distortion and the sub was very localizable. This test of course was nothing more than to satisfy my own curiousity and does not represent any practical listening scenario.
This is a home theatre as well as musical sub. During movies, your entire house will be shaking and you'll still have lots of room on your volume control. For music, you will be very satisfied if you like your bass smooth, transparent and enveloping. The sub blends in beautifully with the other speakers and it does not mask the rest of the music. It plays transients but can also maintain a sustained note when it's called to do so.
What this sub has not been able to give me thus far (and I'm not done tweaking and experimenting) is the realism in percussive sounds. I've come to understand that a sub should hit you in the chest as well as the bowels. The 600 delivers on the bowels part...that's the low and transparent sound that I referred to above. But the chest part is lacking. What's missing is the rise time associated with the sound of the drumstick hitting the drumskin or the fingers releasing a string. It's the slap, thwack and ping that's missing. These are not deep sounds that I am referring to. They are higher frequencies that this sub is not able to produce because it has a steep filter above 100Hz. My M80s can somewhat compensate for this but they have to be turned up very loud and this is not something that I personally enjoy due to my extremely sensitive ears.
The other thing that I can tell you is that a lot of thought has been put into the driver. It's very heavy due to a very large magnet. The voice coil is cooled by conduction, radiation and forced convenction via a large hole through the centre of the coil but also through four smaller holes on the outside circumference (see picture). When the driver rarefacts it sucks cool air into the coil and when it compresses it pushes hot air out of the coil. This is very important because proper cooling minimizes driver compression and preserves the original design parameters of the coil. The spider is very well constructed and the cone, being made of aluminum, is very stiff to prevent distortion. It also has dual voice coils connected in parallel for maximum current delivery out of its amp. And the amp runs very cool which should make the electronics reliable. The basket is made out of a composite material so that it won't resonate. And the surround rubber is extremely durable. I expect my 600 to last a very long time due to its excellent construction.
You may also want to look at Illka's sub test
site before you make your decision.
