Okay, try this out. First of all, Pioneer h/u's don't really put out a good pre-out voltage until mid-high 50s on the volume. They also don't usually clip until almost 60 (assuming loud, bass boost and shit is off).
Not sure how you have your settings on your h/u, but I suggest you reset your gains like this...
Volume at 55 (trust me on this), SW out turned on (obviously), SW level at +6 or all the way up, loud off, bass boost and all that other bullshit turned off, eq set flat. Once you've set it like that, recheck your voltage with your DMM (set on Vac / Vrms) and see if you're not getting your desired voltage at closer to half-way on the gain knob. If not, your amp must be fukked up or extremely overrated.
Now, if you're getting a good voltage from doing that, and your idmax still hits like a little bitch, try reversing the phase. You can do that on your h/u. Another thing to mess with is the eq settings. I believe that h/u has that wierd eq where you select a frequency, then the Q or some shit. That could be another solution. Also, make sure the LPF on your h/u, not just your amp, isn't set too low.
Good luck