Stating a software firm.

It depends on the type of "software" company you run.

If you own the technology, you will need to find local Italian customers which means hiring Italians to do the selling. This will require significant startup capital (payroll 60k Euros in the first year as example). If you feel you can do that, I think some in the Italian government will actively help you (especially with regards a Startup Visa). As a note, the Startup Visa is very stringent on the type of business you can open, and you also need demonstrable proof of at least 50k funding.

If you're one of the myriad of freelance / outsource companies, there are a number in Italy who do very well. I applied to one for a job the other week. If you are looking to open a "branch" in Italy, the only thing I would recommend is to contact a lawyer who knows how to approach the matter. Expect to pay $$. With regard the marketing in this space, it's my experience if you don't have Italian customers already, you need to make finding them a priority which to me suggests you need to hire some locals. Of course, already having Italian customers will justify the move with the government somewhat.