My only advice is to book FAST. The best places/ best hotels/ best deals seem to go fast (well, at least the ones I was looking at. I haven't travelled a whole lot though. I've been travelling more in the last few years. I now book several months ahead, even a year.
Been to Italy, you can't go wrong with Italy. Have not been to Amalfi Coast but have also heard what CanuckG35 said about it.
Here's a thought for a veeery relaxing type of travel: european river cruising. Pricey, but I highly recommend it for a special occasion. I totally hate having to do any work/research for vacation, I'm a workaholic until the last minute, and I just want to board a plane and have everything done for me. So the "pack/unpack-only-once-and-have-everything-planned-for-you-but-you-still-can-decide-what-you-want-to-do-every-day-yourself" kind-of-trip that the river cruises offered was perfect for me (and fortunately hubby too). But that's just me. If you and your fiance might like that kind of stuff, I highly recommend Uniworld Cruises. Top notch.
EDITED: Typos, bad grammar.