Yes, I have...
I have an amp under the floor in the rear luggage bay, and a sub under the dash. If you have a look around the roadster owners club forums, you'll find various ways of installing ICE without sacrificing your storage area. www.mr2roc.org
Hmm, this looks like something I'm going to need to check into as well. I was thinking about fitting 6x9's into the lid of the luggage bins, but I need the seat right back so I fit into the car - there'd be no clearance for a speaker