Hi Dave:
I looked at the Owners Manual extensively and could not find anything about the speaker output. There is a line out opposite the line in. The Aux-in is a 3.5mm connection and I am assuming the Line-out is the same so it would appear to be a signal level which would be a pre amp output versus speaker output so you would either need powered speakers or an external amplifier and then you could connect to the RS-670 Rock speakers.
It might be worth while contacting BOSCH tech support to get a more definitive description on the line out.
TL/4111