You may need longer than 6 hours, 7 hours or more. If you go on a weekend, the trip might last much longer: Long pile-ups between MUC and Innsbruck and again at the Brenner.
If you have a car, you need a hotel with parking. Hotel Royal is such a hotel. In 2001 I did not like the 3 rooms I was shown, and we went to Fiesole just "on top" of Florence.
However, I know, Hotel Royal has some nice rooms; facing the garden.
You find the address etc. at Michelin.
See that you get a car with (turbo) diesel. And make sure that you can take the car to Italy. Last time I made them change/addend their documents.