I stayed in Villa Sonnino because I just found it by browsing booking engines... but what a marvellous discovery it was! The Villa is somewhere in between a museum, a renaissance villa and a fairy-tale castle. What's more: it comes with a gourmet restaurant, so no need to go out in the evening. When I looked at the price of the hotel room and restaurant bill the following morning, I thought there had been a mistake, but no: it's just very inexpensive. This must have been one of the best price/quality scores ever in my lengthy Italian hotel experience.
The only small downside is that you need a car to get there, but that applies to just about any place in Italy outside the city centres.