Clownfish,
You have some Vintage equipment. The JBLs were 1988-1992 and were rated at up to 200 watts. JBLs used to be very good speakers so I am guessing nominal impedance of 8ohms and average sensitivity ( 90dB).
If the Kenwood receiver (1992)still works I would use it, it is rated at 130 watts per channel (in stereo only mode, otherwise 80 watts per channel) and should easily drive the speakers. However it only has RCA left/right analog input and no sub or LFE out.
Here is an online copy of your Kenwood manual
http://inform3.kenwoodusa.com/manuals/KRV8540.pdf