I trust the budget is $3500 each, not combined. That is about 2400 euro, more or less, since the exchange rate varies. So I think the budget may be a problem for a three week trip.

If you are flying into Amsterdam and home from Rome, that will save a bit (both in time and money), but if you have not already bought you airline tickets, you will be in for an expensive shock, since you are flying in high season and buying at the relatively last minute. I would not be surprised if your airfare is well over $1000 each.

A car is nice in southern France in the countryside, but you aren’t going there; you are going to fairly large cities. I wouldn’t rent a car in that situation because you won’t really need it, and the parking, gas, tolls, and a hefty drop-off charge (imposed when you pick up the car in one country and drop it off in another) will be a big expense.

Finally, I know a lot of people like to see a lot of places, rather than a few, but you should realize that when you travel that way you won’t see much of any place but train stations, and you will consume a lot of your time on relocations. My suggestion is to save some of these places for another trip. Two days in Venice and three in Florence is minimally sufficient, but 3 days in Rome, and 2 in Paris and Amsterdam is, in my opinion, too little.

It’s a little bit rushed for my tastes and I wouldn’t do only two days in Paris but three in Florence, but I guess it depends on what you really want to see. I’d skip the one day stops in Marseille and Nice to add more time elsewhere, and definitely wouldn’t drive this part of the trip. Renting the car in France and returning it in Italy and finding/paying for parking will be an expensive pain in the a**. I’d fly from Barcelona to Pisa (book now for as little as $50 depending on your date), grab the train from Pisa to La Spezia, and then make the short train trip to Cinque Terre from there: http://www.visitinge…

Just returned from a month in Italy (don’t be jealous) and have to say the Cinque Terre was probably the best part. I would book a min. 3 days in the cinque terre. This will give you time to relax, maybe spend a day hiking between the various towns ( the trail between Manrola na dRiomaggiore was closed when I was there). Florence for 3 days is maybe too much unless you are heavily into renaissance art, otherwise I would rent a car and get into the Tuscan countryiside (maybe a day trip to Siena).