We have an old Kenwood audio-video stereo receiver (KR-V7040) with 2 wired Bose speakers. I would like to add 2 wireless speakers to get a surround sound feel. A friend told me about Sonos Connect- but it's really expensive. It WILL work with our wired speakers once installed to our receiver but it's only compatible with Sonos wireless speakers...which means even more $$$$. Is there a system out there that is the same idea but more affordable?
Sonos connect will not give you rear channels. It would add streaming services and audio file playback if connected as a source for your receiver. You don't use Sonos speakers with the Connect.
The solution that jsmithpa presents will give you stereo out of the BT speakers but not surround sound.
If you connect a speaker to line level converter to the rear speaker outputs that will give your a rear channel output that you can use for a BT transmitter. https/www.manualslib.com/manual/777432/Kenwood-Kr-V7040.html
In either case you will need a transmitter that can pair with 2 speakers. Most will only pair with one. You will need to balance the rear speakers so you get the right amount of surround sound. Follow the receivers manual. Set the volume of the BT speakers as high as they will go without any hiss or noises coming from them. Adjust the rear channel output of the receiver to balance to the front.
You can find the manual here https/www.manualslib.com/manual/777432/Kenwood-Kr-V7040.html