My 7.1 setup is based around a Harman Kardon AVR 525. Try as I might, I can't seem to get sufficient sound from the surround backs. To establish sound levels I'm using the HK Remote Control SPL utility.
Are you talking about from true 6.1 DVDs or all the time(like even with psuedo-6.1 where it's deriving the surround back information)?
Placement issues and the source could effect the results. How do you have the speakers set-up relative to your main listening position? Remebember those speakers aren't supposed to be continually active for DVDs.
If everything else is in order, however, you could always boost the levels to taste.
You might try using one of the Radio Shack analogue spl meters, they cost less than $40.
I've used 3 different "7.1" receivers and used both their self calibration and the meter for the back surrounds. The self calibration actually was very accurate, btw.
What I've found in actual use is that even with the back surround levels properly calibrated there aren't many dvds, even DTS 6.1 discrete ones, in which the back surround channels are used in such a way that the sound can clearly be localized to those channels. Even those few that do have sound distinctly coming from those channels only have the effect in a few scenes and very briefly. The Haunting, the LOTR films, Gladiator, and Open Water use them a bit more than most other 6.1 mixes, haven't tried the new Top Gun SE yet.
i have the h/k 320 that has the option for 7.1 also. for mine i have a seperate 100watt 2 channel amp power them. i dont know if you have a seperate amp but i think you need one to run the speakers.
That will also make them louder and more noticable