I think I posted about something like this a while ago. I strongly recommend incorporating a Harmony hub with Echo Alexa for interfacing with stereo and other equipment. I then use Echo and Echo extensions (like Dots) as a voice control system which handles the requests to the Harmony hub to actually control the various devices. Harmony can control IR, bluetooth, wifi and Radio controlled devices.
If you need to move IR signals long distances or between rooms, use IR extenders and blasters as required.
Combinations of all of the above give a lot of flexibility in design and execution of commands.