I posted a thread a bit further down, which got no responses, about my Alpine amp not working. Turns out it was the RCA preouts on my head unit that are bad. The only alternative I've found to shelling out another $100 for a new head unit is something called a RCA Line Out Converter.
Does anyone have any experience with these? Would it be possible for me to split the connection running to my rear speakers and run it through a line out converter to the sub without degrading the sound quality and/or wattage that's getting to my rear speakers?