Take LOUD off. If it's the sub "pre-out" level control on the HU...set it to +5. Pioneers have -6 to +6 correct?
You want to be getting near full signal from you HU pre-outs, so set it the Subwoofer pre-out level to +5. (Not the bass/treble level thingy). Unhook your speaker wires, Pop in you 0dB test tone CD, drop it on 45hz and pause it, set you volume to near the loudest you normally listen to music, unpause, and get it to 46v AC on the DMM. That puts you at ONLY 2200watts unloaded, and the 2500d is obvioulsy capable of more.
Oh, and my 15MT is louder than my 18XXX was...daily even...
NG