Im using the 4000 Stinger ones to my 4 channel amp and the higher end 8000 series to my mono amp. Got rid of the engine noise, the wining was driving me crazy =)
Yea it is 2 volt headunits are cheap and have no were near as many adjustments as the higher end 4 volt HU. I've set all my car audio gear up, my one 12 hits 140 db on music not generated tones