i added it for a 4 channel amp and a 2 channel amp. I have front rca going to front 1/2 of 4 channel, and the rear going to sub amp, which has a full range pass thru that goes to rear 1/2 of 4 channel amp.
confused yet...lol
anyway, I tried y-cables, but that was a FAIL....lol
Also the way i have it now, I get true front rear fade and true left and right balance.
Would like to move to a 2 in, 3 out crossover, and then run front and rear to 4 channel, and sub to sub.
For your application, you should not hear any feedback, and should be fine. When you decide to add power to your doors, then you will have this issue unless Im just that unlucky..
Good Luck
Send pics