Dividing power between different speakers from single source & Combining channels

[Fusion-One]

I was recently given an oldschool rackmount monster of an amp. An ALS model 1500A. It was from an old club soundsystem, and was juicing 8 250w 12"(6ohm) subwoofers. It weighs 150lbs!

My plan is to make an inexpensive sound system using components from mach5audio.com

I'm thinking to mount the amp in a 1" ply birch horn, with a single 600w 18" sub.

I'd like to also have two satelites, each containing:

1x MAW-12" (350w)
2x MLI-6.5" (100w)
1x 4" Belisle bullet tweeter (70w)

My real question comes down to this:

How (is it possible) to route the power between these speakers from the two stereo outputs of the amplifier.

I want to divide the power coming out of this stereo amplifier like so:

Mono:
500w to the 18"(8ohm)

Left Channel:
300w to the 12"(8ohm)
150w to the two 6.5"(8ohm)
50w to the tweeter (8ohm)

Right Channel:
300w to the 12"(8ohm)
150w to the two 6.5"(8ohm)
50w to the tweeter (8ohm)

Is there any way I can do this? I tried searching but I could not find any info on how I could route the power like this, especially how I could send mono power to the single 18" speaker (i.e. combine two channels) without sacrificing stereo entirely.

Am I dreaming here, or is it possible to route the power how I'm thinking?

Many thanks for any responses.

-Jared

I was thinking for the combining signals without losing the stereo, I could use some sort of low-drop diode system?