I have a Pioneer as well. I set my sub level at 0 db when im pounding, but for daily I have it at either -6 or -4.
My premier pioneer (2 years old) has 2v pre-outs. But in order to get the full pre-out voltage, at least at mine, you have to have sub level all the way up, and volume all the way up, which gives you distortion out.
My actual voltage out to my amp is .226vac, no joke. On the HU volume, it goes up to 62, but I only turn it up to 45 max (with loud sleceted to high) to mantain some of SQ.