In my room, at movie listening levels, I get good output (80 dB) as low as 13 Hz. At music listening levels, I get the same output at 17 Hz. And that's with the 600 gain at 7 o'clock (ie. lots of room to spare) and the LFE gain on my Denon at -6 (it goes up to +12). I'm suspecting but can't be sure that my low end is limited more by my bottom-of-the-line Denon than my sub.

I'm not sure if the 500 would go this low. Also, the 600 cuts off higher than the 500 I think. This isn't important in this case but for those with book-shelf speakers, this may make a big difference.