Ah, I forgot to take in consideration the distance and that's why I don't get 75dB. I understand now, thanks. I sit at about 7.5ft.
As for the fronts being slightly higher, it might be due to how I was holding the meter. I'll try on the tripod facing up as Michael suggested.

Bruno
M80s/VP180/QS8s/EP600/AVR-890
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"The problem is choice..."