I'm going to be upgrading the stereo in my boat. The marine head unit in there (I'm not replacing it) has only one set of RCA outputs. I will be running a mono amp and a jl audio 6 channel amp (e6450). Can I go into the mono amp, then back out through the output on that amp and then "Y" into the rca connections required for the JL audio e6450? The JL needs 2 sets of inputs - both on Ch 1&2 and 3&4. It can take the sum of those to configure Ch 5&6 without rca's. I have attached a diagram to help explain what I'm talking about. Thank you in advance for taking the time to help me out.