Catania is in Sicily, so not suitable as your sole base unless you want to spend all your time on that island. Where do you want to go in Italy, and what are you hoping to see?
Sicily itself is large enough that Catania is not practical as a base for seeing the entire island. I suggest that you go to ViaMichelin and check out driving times from potential bases to possible day-trip destinations so you know what you're setting yourself up for. If you plan to use public transportation rather than renting a car, you should figure that travel time is likely to be considerably longer than the private-car estimates provided by ViaMichelin.
There really isn't such a thing as a "euro train system". Each country has its own trains; many countries have multiple rail companies. If you're contemplating rail passes, I'd discourage that. They're seldom a good deal these days (especially in Italy), and for folks planning a stay-put vacation, a rail pass would almost certainly be a waste of money.
Although Sicily has some train service, it is somewhat limited. You'll probably end up using buses a lot.