Not sure what your price range is but since a high end one has already been recommend let me suggest this one, Hotel Bretagna, on the Arno within sight of the Ponte Vecchio. Hotel has been undergoing a total renovation so should be completed by now. Most likely was a palace at one point in its life and service is really good as well. Price is a bit more reasonable and the renovated rooms overlooking the river are fantastic. Some even have balconies. A double superior with river view should be priced very well in October. http://www.hotelbretagna.net/

va bene
Sam