There are a number of possible routings between Paris and Milano. Geographically, Paris-Lausanne-Milano-Florence may be the shortest, but not the fastest. Other possible routings are via Basel, Torino, the Mt. Cenis tunnel, etc.

According to my schedule, the quickest way (10:30) is to take one of the two daily Paris-Milano TGV, then a Milano-Florence ETR or IC train. The TGV will run on high-speed tracks for only an hour and a half (in ten years or so, depending on politicians, a TGV line may be extended all the way to Italy). However these are day trains.

The only directs are night trains, which take about 13:30 hours.

A day train will save you the sleeping car fee, but you will lose a day travelling. If you are a sound sleeper, a night train would probably cost less than a good hotel, and give you an additional day of sightseeing.

As for the lowest fares, they would be advance purchase fares bought locally, with whatever discount one qualifies for, and at non-peak periods. None of the major European railways' websites calculates a price online for an international itinerary, to my knowledge.

Two of the better ones, for scheduling purposes, are the Swiss and German ones (they work Europe-wide):
http://www.rail.ch/pv/index_e.htm
http://reiseauskunft.bahn.de/bin/query.exe/en

[This message has been edited by monahos (edited 09-03-2002).]