I started doing some tweaking with my Sentinel. For most HT it sounds pretty darn good and with some types of music my system sounds fine (acoustic music: folk and the like) but others just sounds kinda washed out (basically hard rock and heavy metal).
I downloaded some test tones (been too cheap/broke to buy a sound meter yet). I played some music to adjust everything to comfy listening levels for comparison (-25 on my Harman Kardon AVR 254). Just by ear I discovered that there isn't much output in the 20Hz range, decent in the 30s, a big spike at 40Hz, and then my system has a major null at ~100Hz. I think one of the damping pads would help down low (I'm getting a lot of resonance with the wood floors) Also, I think the null at 100Hz is what is making the music seem thin--especially heavy metal because thats where a lot of the driving guitar seems to fall. I'm gonna try upping the crossover on the speakers to 100Hz from 80Hz to see if that helps fill in the void.
I have to say that I was friggin' amazed how much the base did vary from position to position--especially the dead zone in the center of the room.