If my wish was for a 975 but with 2 HDMI outputs (vs. the 1 that it has) would combining this with the HDS-42AVR solve that? I would not be using a 4K/UHD television (which is a use for which it is being touted).
The short answer is no. You would still have to split the same HDMI signal to the HDS42 and to the 975.
An HDMI splitter could be used at the 975s HDMI out.
I haven't tried any of these, so I can't recommend any, Don't know how well they work, or if there would be handshaking issues. Maybe someone else could offer their experiences.