The home stereo tool I want the most

I have no idea if this even exists. I tried some random searching and I haven’t seen anything like it yet, but it’s pretty straightforward.

I want a device that works like a wireless phone system, but for speakers.

1 “base” unit that has a USB cord for my computer.

1, 2, 3, 4… units that all have stereo audio out & digital audio out that I can plug into a basic amp or receiver.

Then a little selector on my computer that says what speakers I want to use.

[Update: You can sort of do this by buying a bunch of Apple AirPorts, but I was hoping for a solution that costs less than $100 per room. ]