Using old amp as power amp in surround audio

I have tried this a long time ago in the past and ended up buying a sony 5.1 receiver that has 5 built in 110watts rms/ch amp later.
I had a Fleetwood console stereo with a then newer surround dolby receiver.
The console burnt out a tube one day and died. The old console had a bit more power for 2 channels as the newer sony 5.1 that boasted 110watts/ch. I continued to use the fleetwood's speakers until i gave it away when i moved. The old fleetwood with built in 12" drivers sounded great and had awesome bass. The tube amp was cleaner and sounded better than the sony.
You might want to switch them around and use the newer and likely less powerful amp for the rears and the older one for the front channels.

-You will need two 1/8" to rca cables.

1. Connect the newer one so it goes from your soundcard's rear channels to the newer amp's front channels. Set it to run in stereo mode or 2ch mode.
2. Connect the older amp to the front channels and speakers.
3. You will have to adjust the volume so changing the volume on the computer controls the volume for both amps. Setting it to high will cause hiss when the volume on the computer is turned down. You will have to find a spot where it sounds good without too much hiss.
-Some things on the older amp like the loudness button, and better filters and circuitry might make you want to consider using the older one as the front channel amp.

I would try both amps first as a 2ch stereo amp for your front speakers to find out which one sounds better with more power. The rear channels do not need as much power.