A couple of good suggestions and when I try DL again, I will try adding some gain on the calibration page to the surround speakers. The multi channel preamp idea might also work but not sure i want to go that route as I am trying to simplify the system.Dirac on its own won't raise a speaker above 0dB, but you can do that, up to +10dB, on the Calibration tab, in the User Trim column. Several of us were having the problem of having to raise the Master Volume several dB after a Dirac calibration because we had certain speakers, usually Surrounds, that were much quieter than the mains. Dirac would attenuate the mains by as much as 15dB or more to make them match the Surrounds. Some of us fixed that by adding tiny pre-amps to our Surround-channel DIY power amps.
I think I remember hearing about some potential issues with going above 0dB in the User Trim (eating into headroom, or something like that) but I'm not smart enough to speak intelligently about that. I've done it to a degree, and my head hasn't fallen off.
Hope this helps.