Sorry, I don`t think, you can upgrade from 1.6 to 2.61a, because Cheetham has the "old" BL5, the "non-pincode-version". They have SW 1.xx
The newer ones ( with pin-code) have SW 2.xx. So the latest SW should be 1.61a. My BL5s were updated with this one and to answer your question, I have NO problems with these speakers.
Stefan