Parasound P5 McIntosh MC402 mismatch?

I just replaced my parasound a21 with a mcintosh mc402. I am running it through a parasound p5 and while the sound quality is great the volume is not what I expected. Considering the MC has more I'm confused as to why this is happening. Thoughts?
It appears that if the 8 ohm tap of the MC402 is used the two amps have essentially the same voltage gain. So if you are using the 8 ohm tap I don't know what might account for the lessened volume. However if you are using the 4 ohm tap or the 2 ohm tap of the MC402 (which you would want to do if one of those taps is a better match to the impedance characteristics of the particular speaker) its voltage gain will be somewhat less than that of the A21, requiring you to turn the volume control on the preamp to a higher setting than with the A21 to achieve the same volume. Assuming, as is likely in most cases, that you don't find yourself ever wanting to turn the volume control up higher than its maximum setting I wouldn't consider that to be a problem.

I'm assuming, BTW, that you are using the same type of connection (balanced or unbalanced) with the MC402 as you used with the A21, and that the balanced/unbalanced switch on the rear of the MC402 is set correspondingly.

Enjoy! Regards,
-- Al