I did not work on the Crossfire, but I did work with the six channel amplifier that is in the Crossfire. It is the same six channel amplifier hardware as the full size Dodge truck (2003 as I recall) with different equalization parameters. The amplifier input is four channel balanced. It is designed to accept speaker level signals into the DAC. The Crossfire harness Y-connects the radio speaker terminals from four wires out of the radio to eight entering the amplifier. That is the left front output pair of the radio goes to both the front and rear left input terminal pairs of the amplifier. I seem to recall only a modest amount of gain the the Crossfire parameters; just enough the amplifier input won't clip before the 6 channel amplifier does. The input circuitry in the amplifier is designed for speaker level signals as in the classic car audio "booster amp" configuration. RCA connections are unbalanced and therefore not recommended, though the amplifier may work okay with them. The amplifier balanced input circuitry is very good. Bear in mind that "line level" and "speaker level" voltages are nearly the same. The difference is speaker outputs have more current capacity. Your new aftermarket radio may have four channel speaker outputs and a front/rear fade control. Be sure you connect only the two front channels and insulate the rear output terminals (or wires). Then set the fader on the new radio to 'front'.