Hmmm, you kinda lost me now.
I pulled up your amplifier
Your amp has both a four channel input and a two channel input, both of which will result in a four channel output.
Can you let me know where you pulled that up? I have the online manual, but it does not state the 2 into 4 outs anywhere.
Connect the radio fronts to one line converter. Run the output of the line converter and the radio's rear RCA to the channel 1-2-3-4 inputs on your amp.
OK, I understand this. All 4 RCA amp inputs would be for the radio.
Connect your radio's amp trigger wire to the coil of the SPST relay and also to the amp turn on terminal. Run the 12V power supply connection for you tape deck through the normally closed set of contacts on the relay.
When your radio is on, it will open the 12V supply to your tape player so that it cannot be turned on. The radio will turn on the amplifier and your fader will work.
When the radio is off, the tape can be turned on. The line converter will turn on the amp. It will play through all speakers but will be non-fading.
It would be best to set up the gains on your amp to get the best front/rear mix with the tape and leave them there. You can use the radio's fader to adjust the mix when you're playing it.
I understand this section too, but I have to look a little closer at the relay specs.
Connect the low voltage trigger line converter to your tape player. Run that to your amp's 1/3, 2/4 inputs. Connect the 12V trigger line to your amp's turn on terminal.
This is where I am having trouble. After the RCA inputs are filled, that leaves the 4 channels of speaker level inputs and the 1/2 3/4 pre-amp outputs for a sub (which I may do later)
11 Pre-Out Jacks (MRP-F200 only)
These jacks provide a Front + Rear summed
output (Non-fading ). This is an ideal output for
driving a separate subwoofer amp. This output is
full-range, and is not affected by the crossover.
I could not find any 1/2 3/4 inputs.