You guys were right...this second hand, second generation MP40 is quieter than my recently sold MP10. It leaves NO dead spots in my barebottom 40g breeder.
It does still whine @ ~66dB at full speed. For frame of reference my skimmer has a relatively quiet pump and it runs ~67dB.
Now the whine from the MP40, though 1dB lower, is more noticeable than my skimmer's pump.