Classe Processor and Amp

I have a SSP800 and had similar problem.. When setting the balance between R & L speakers using an SPL meter , they say to set the meter to C weighting, slow response, and 75db range.. Unfortunately the meter app I downloaded on my smart phone can't be set at 75db.. 70 or 80 is the settings I can use... First I did the 70db and found the volume was low like how you described (but not as dramatic).. Next I used the 80db and that solved the problem.. Another thing that came to mind is - can your SP300 handle the HD codecs ? Try setting the Oppo to output regular Dolby/DTS ..  Also I read somewhere that setting the bluray player isn't a good thing to do because the higher you set it, the bit rate drops... I have my Oppo volume set low and have no problem with the volume coming out..

setting the bluray player to 100  

I have the older version clase sp 25 connected to a Bryston 3B and am getting the same problem, am not using the central channel because is only stereo, can I hook another three channel power to the processor? Hope that way I don't have the same problem 
thx