Looking for a WiFi interface

I’m using an under-$100 consumer BT wireless transmitter to send signal to rear speakers in a 5.1 home theater. This is a mid-fi system in which the ambience channels consist of $500-$1000-ish Cambridge Soundworks speakers connected to an $1800 Audio Alchemy stereo amp. The amp receives line-level input from a $2000 Marantz A/V receiver via the wireless interface. My "serious-listening" stereo is something else all together, T+A / Harbeth / Audioquest Niagara, etc., but this CSW/Marantz/Alchemy setup has been satisfactory for Dolby-soundtrack ambience channels.

Except for one thing: No matter how I position the wireless xmitter/receiver modules, I get annoying dropouts. And if I could improve the SQ even a bit, that would be wonderful, since I’m starting to get into vintage Quadraphonic mixes. AptX HD would be an upgrade, I’m sure, but I’d prefer a WiFi solution.

It wouldn’t be a problem to invest a few hundred bucks (or more) in an interface, but all I’ve been able to find so far are more no-name Amazon interfaces & pro-audio products intended for stage performance. The few name-brand audiophile-grade wireless interfaces name-checked on this forum don’t seem to be in production today.

Can anybody make a recommendation based on first-hand experience? This has got to be a common problem, no?