Mark,
I've bought almost everything I have in my setup in the US.
You are supposed to be paying (in Italy, where you live), two kind of taxes: what's is called "dazio", i.e. custom fees, and IVA (VAT for US).
How much?
It depends on declared value and merchandise category, but it can oscillate between 10 and 35%.
According to my personal experience, I generally have a total amount of 30-40% as overall expenses over declared valued (be careful that they add transportation costs too!

).
But for example a rebuilt 9" tube from VDC went through with 0 VAT because it was a "computer spare part" (don't ask me why, but thanks to FedEx for telling me...).
Should you find April's issue of Digital Video Home Theater, I wrote there an article with some suggestions based on my own experience...

.
Hope this helps!