@Vincenzo -- The same principal applies for bass amps or keyboard amps. Those are made with specific interests in mind and don't mix and match all that well. There are exceptions, but the general rule is to buy an amp made specifically for the instrument you want to amplify.
By the way, if you are buying an acoustic guitar amp play it loud in the guitar store to test it. The problem with acoustic guitars is that they are hollow and that can result in terrible feedback (i.e., squealing) if an amp is not built to deal with that.