Second Ceiling and Fiberglass Insulation

I have a second story room with a vaulted ceiling. The room is difficult to heat and cool. During the winter snow melts off part of the roof of the room while the rest of the house remains snow covered. Only R-19 insulation was installed in the ceiling because that's all that would fit, and that included furring strips to build out the 2xWhatever they are.
For the moment I decided to elliminate the vaulted ceiling and install a standard 9 foot ceiling with R30 fiberglass bat insulation. I see no reason to go beyond R30 since I already have R19 up there, plus the additional dead air space created between the old and new ceiing.
So finally here are my questions: Does anyone know of a better or least costly way of increasing the insulation using the existing vaulted ceiling? Ripping down the drywall to extend the rafters would be more costly than building a new ceiling. I don't care about preserving the vaulted look. What I need is something like foam insulation sheets, but something decorative. I've seen insulation sheets at Home Depot with R-Values up to R20. If they were decorative, maybe they could be glued to the existing ceiling drywall.
If I go the second ceiling route, should the insulation be with or without a vapor barrier? Assuming the existing insulation has a vapor barrier directed toward the room, is there a problem with a second vapor barrier above the new ceiling on the conditioned room side?
Thanks for your comments.
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Paul wrote:

have you thought about putting up the insulation sheets and then going with one of the acoustical tile ceilings?
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