Help with Audioaccess W.H.E.N.

Longtime lurker. Rarely post, but figured this board could help. Looking at a home purchase that has an Audioacess WHEN system built in. How user friendly is this system? It doesn't appear to have HDMI input/output on the 7.1 receiver. Does anyone know if it's easy to upgrade the receiver without making the remaining components useless (multi room speakers and controls)? I could ultimately mothball the multi room wall panels and speakers, but would like to continue using them if possible.

I intend to get an AV person to check it out as part of the home inspection process, but also wanted to see if this board had any opinions.