i just purchased an audio control EQS, sweet unit. The three.1 is also a good unit, but you do sacrafice flexibility and adjustability to have an in dash unit. The EQS is pretty much Audiocontrols best piece, before their digital stuff, which gets VERY expensive. It is a 6 channel (front L & R, rear L & R, sub L & R) EQ, has RCA and speaker level inputs (yes, you can use it with a stock deck, even Bose), subsonic filter, line driver (with the same 13 volt max). Its a very slick unit, I have yet to install it, as I just bought it today, but i'll post my thoughts once its in.