Anyone upgrade their interior and exterior speakers?

Can you post up what sizes are involved? I build some audio stuff and may have a recommendation for you. There has been a fairly large leap forward in small, full range speakers in the last few years. Some of these can have great sound quality.

FWIW, I went with a 120V system since I had all the pieces on hand and have an inverter powered 24/7 but near the same quality can be had with 12V. The RV makers decided, just like the auto makers, that the cheapest speaker that fit the location was good enough. Even the stock premium car systems haven't attained the quality available to a DIY guy.

From pix of different units I see that most of the ceiling speakers seem to be flush mount. Mine are canted, almost aimable. Haven't had time to pull one but I wonder if they are any better?

You're trying to force a single cone to accommodate a wide variety of frequencies. At least go for a 6x9 with a separate tweeter in the center; some will even have a separate tweeter and mid in the center leaving the big 6x9 cone only for bass.

I wouldn't say marine is a necessity--there are a lot of good name speakers with polypropylene (instead of paper) cones that would resist moisture (but not rain) for a lot better price. You pay a lot for marine and don't necessarily get a ton more weather resistance.