I live near Geneva, slightly outside the published footprint. I can get Channel 5 without problems on a 60cm, albeit with little rain margin. With 90cm it's rock-solid in everything but the heaviest rain. I am a long way from Tuscany, so my experience is little indication of what would be needed now,
and even less indication of what will be needed in the future. Your best bet is to wait until after the latest round of satellite shuffling and see what changes other people with currently-installed systems see. For example, you'll look for posts saying "I live near Florence, I could get Ch5 with an Xm dish now and now
see nothing/see no change/see nothing but my friend down the road gets everything on a Ym dish".
Or you could run out now, guess, get solid reception for a few months then either have to splash out again on a bigger dish or possibly get lucky and still be OK. Your money, your choice