@kem, since the Plantronics only goes up to 6800 Hz, your audiologist should be able to get either the volume or clarity that you need from your Resounds. There are a lot of Bluetooth phones but I cannot help you with the one that may work the best for you. Ideally, a properly tuned hearing aid should give you the best performance. I take it you plan on using it like your Plantronics (without using the hearing aids). Here's a place in Michigan that sell Hearing Assitive Devices:
https://www.harc.com/collections/bluetooth-phones
Tony in Michigan