I used Boston Acoustics patio speakers mounted to the rollbar right behind the rear jump seats. With the hard/soft top on they sound great and fill up the car with tunes, but with no top it can be hard to hear. They are very durable, having lasted about a year of all weather abuse. I do not know if I would use them if I had to buy them, $350 is a bit much, I got them for free from a friend.
Edit: Mine are in nearly the exact same place as Pimp's, just about 6" lower, and bolted directly to the rollbar, I would rather use those cb mounts if I knew about them.