Fixing my system on a tight budget.

Before the world went pear shaped I was in the process of putting together a new cinema sound system in my living room. Currently I have a Marantz AV7703 pre-amp and my plan was to build a nice multi channel amp to plug into it.
Currently my amp is an old yamaha dsp75se receiver just using the multichannel inputs.
So my question would be is it possible to rip out just the amp part of this receiver and utilise it as a slightly better amp for my speakers. I have had a look at the service manual but cant get my head round it. The Yamaha amp is very old but until the world gets back to normal i'm in no position to spend big money building a good multichannel amp. So I think my best option is to try and make a multichannel power amp from this old Yamaha receiver.
 
Yeah it is,, sort of i my opinion. I would like to get everything completely bypassed like volume control and other bits so its just a pure power amp.
I'm simply trying to make the best out of the what I have at the moment.
Also it looks awful sitting below my marantz 🙂