At Motorway speeds the stereo is a bit pointless but at anything less the 100 km/h (60 mph) it is nice to have some MP3s playing on a USB Pen Drive. A pity there are not a couple of small speakers installed next to the seats though. They could supplement the foot well speakers nicely.
I guess it really depends how you use your Morgan. If you use it for short sprints maybe a stereo is not worth while but if you use it for touring, the way we do, stereo and aircon (yes we do use it in the summer heat) are well worth considering.