I still have a speaker on my GSA crossbar......it's plugged straight into my Quest cradle.
I put it on an old Funduro I dis a bit of despatching on in London....mainly as an easy audible alert for turnings coming up.....I didn't want to be wired to the bike physically and looning around at the speed you have to keep up to make any money takes a lot of focus on the traffic/roads, so although I couldn't hear the voice commands properly, the beep it made at least let me know to glance down.
I moved it onto the GSA for long tours, for similar reasons......it would be hopeless to listen to music on, but again, the beeps are enough to catch the attention to the GPS.