Probably a dumb question but can a 568 be used in conjunction with a stereo analogue preamp?

- I want to use the 568 not as the main preamp hub, but only when I watch movies.
- When I listen to stereo I want to use an analogue stereo preamp, and the 568 could be switched off altogther
- I have a Krell preamp with a 'Unity Gain' input, for 5.1 use. This input takes analogue-only volume increase/decrease directly from the volume control of another pre/pro, (in my case, the 568)and passes them onto the stereo amp.
- When I watch a film, the 568 would then also operate volume and sub levels normally into a separate 3 channel amp I have.

I could accomplish relatively seamless control of the units together using a Pronto.

The only thing I see not working in this configuration is sub control, because the 568 would be 'off line' when only stereo is in operation. I could get around this by sending a preamp out to the low level input of my REL sub, I think.

Can anyone see faults in what I'm suggesting?

Thanks in advance

Paul