i have a HTPC running Kodi plugged into my AVR via HDMI, and then my AVR is plugged into my projector via HDMI.

i can reach the Kodi portal from anything on the LAN, and listen to anything i want w/o the projector being on. Kodi supports local music, and has various streaming music sources available. although i'm not sure about Pandora or Spotify.

it sounds like you need a HTPC plugged into the AVR as one of your sources. switch to that source for audio content, and then control HTPC over the network. Even a RP4 can easily handle your list of streaming sources.

you may want to try a RF / IR repeater, gives you more flexibility with placement maybe ?

https://www.amazon.com/Sewell-Direct-Wireless-Repeater-Extender/dp/B074CNWJZV/

are you sure you had the emitters correctly placed with your original IR repeater ? those are usually pretty reliable.

No. I'm not aware of any similar wi-fi product. Not sure if this one is any help if nothing else work.

Sewell Direct BlastIR Wireless Pro IR Repeater, Remote Control Extender Kit (IR Emitter and Receiver) https://www.amazon.com/dp/B074CNWJZV/ref=cm_sw_r_awdo_navT_g_PMQEGYXE3BD3DESR851F