This is an old thread, but I thought I'd update it in case others are still looking for solutions. We all know the problems associated with putting tunes in a Healey. In my case, the car is positive ground, which limits my choices in stereo equipment. Although I know that positive ground "retro" radios are available, there just didn't seem to be a good spot to mount one and I wasn't sure it would look all that good even if I found a spot.
In an earlier post I brought up the idea of using bluetooth speakers,but there was some concern expressed that they might not be loud enough. After some research, I purchased a set of these speakers for $55 -- Creative D100. The speakers connect easily to my smartphone and are powered by 4 AA batteries, so there's no electrical connection to the car. Battery life is supposed to be 25 hours, and I have at least 5 hours on my first set of batteries.
The speakers look pretty good sitting on the tranny tunnel, and I used a little velcro to keep them from sliding off every time I took a fast corner. They can be easily removed to prevent theft or to use them for other purposes. And they are loud. Loud enough to be heard at 60 mph with the top down, which is pretty remarkable. The volume can be easily adjusted on the front of the unit, or from the smartphone or whatever bluetooth player you're using.
So far, I'm pretty happy with this solution. It required no modifications to the car, it was relatively cheap, and it sounds pretty good (except when my son plays rap through it).