Just be aware that there is a reason the Sheraton Bologna is so cheap. It is really in the middle of nowhere and not in the city proper. Either you have a car to drive into town or you have to take the hotel shuttle to the airport and a bus from there into town.
that hotel also jumps to a price of €250+ if there is a big trade show at the fair. it is an airport hotel. driving into bologna is not as trivial as it sounds. very difficult to park. lots are very expensive.
i have stayed at the palace, roma, and due torri for a few days each. all are in the central old area, which is nice. all are the weakest 3* hotels i have ever stayed in.