Slimline amp, under the passenger seat. Done right, can still move the seat back and forth. You won't get a huge amp to fit, but get a good qual one, you will be ok. It saves a lot of wiring into the boot etc.

Go for Sony (or other) 2-way 15's or 16's in the doors, replacing the factory's with floating directional tweeters, pointed up at you. That is really the only way without messing with the trim.

Mine is setup like this, pending the empeg, and sounds fantastic. It is hard to beleive the increase in volume and quality, just with a little baby amp and good speakers, still with a crap head unit.

When I get my empeg (ordered)I will be looking into either interfacing with the factory "by-hand' controls (could be tricky, and will likely require the ETM wiring guide (not available in OZ) - or sounds like a better option - Is leaving most there, but replacing the main "button" mode control (cd,fm, tape etc) with a sony control stick. Someone has already written an empeg interface for it, and I figure it is going to fit perfectly into that hole. There is a link on the main site to that project....

I reckon you can do the amp under the seat, the two-way directionals in the door, the empeg in the din, the sony control stick, all without messing with the trim at all, and end up with something very good!

I think the control stick is a must. I've gotten very used to "by-hand" controls, and even when the voice software comes out, dealing with convertibles is likely a no go... (maybe if we end up with bluetooth wireless earclip boom mikes or something....) maybe....
I won't be putting my eggs in that basket, going the control stick.... Still want the service manual, so I can pull the dash apart nicely... Convertibles are always tricky...