Italy went digital a couple of years ago and I think you'll need to have an external aerial to get any reception. Before making the investment it might be worth going to the Rai webpages to see if there is anything worth watching (which you could watch on your computer anyway). Rai models itself on the BBC and has a host of different channels - both TV and radio - as well as educational material (you can learn Italian there), and a good news website.
The mediaset (Berlusconi) channels are the "red top" end of the spectrum, and were used extensively to promote Berlusconi when he was involved in politics. La 7 provides an eclectic mix - I particularly like Otto e Mezzo which is bit like Hardtalk.
There are also numerous local TV stations - but they are generally pretty naff.