Yes. It can be done. Ingredient 1 is a Bluetooth transmitter dongle. Ingredient 2 is an RCA to 3.5 mm (female) "Y" cord for the connection. I have the dongle I linked. Not audiophile (heck, it is Bluetooth), but it works. Your biggest problem will be powering the Bluetooth dongle (runs off a USB). Perhaps a wall-wart and a cable from your AC power if you don't have any USB connections in your equipment.
Your first link is dead. I'm thinking that rather than using the 'B' speaker connections, take the signal from the headphone jack on the front of the 2325 into a bluetooth transmitter and broadcasting that to a portable bluetooth speaker.
What kind of delay would result? If one is listening through speakers plugged into the receiver and then feeding a Bluetooth signal to a Bluetooth speaker in another space, say 20 meters away, would the delay be noticeable? I'm thinking anything more than 1/20th of a second could be intrusive if you could also hear the main sourced speakers...
This would be using the BT speaker outside while the receiver/amp plays inside.
Fixed it (I think). Your headphone jack>Bluetooth transmitter>Bluetooth speaker idea is certainly more direct than using the RCA outs.
There are no RCA outs for the entire receiver, only tape one and two..