We have Eurail Passes we will use, but the Intercity Express (IC) trains I am told need a reservation. I'd like to make that here in the states, but not sure how to do that without purchasing tickets. Are there good Websites in Italy or Europe that could do the reservation part without the ticket? I am not sure if these reservations cost, nor how much, nor if different companies charge different rates to make them. Any input would help.
If you need many reservations, Euraide is extremely helpful and worth the US$50 entire transaction cost.
I actually do not think that you need a reservation for Intercity trains. They are available, but the trains requiring mandatory reservation are the EuroStar (ES) and other fast trains. You can look at schedules on Trenitalia, that will indicate if a reservation is mandatory or optional. Either way, it would be better to wait until you get there, 10 Euro each, and they can be made up until departure, best done a few days ahead.
According to the German Rail website, the ICs from Rome to Naples are subject to compulsory reservations. On the Trenitalia website, under "Journey Details" for the ICs, it says "Reservations must be made in Italy".
As Lee says, reservations are compulsory on IC trains in Italy. The passholder reservation fee is 3 EUR. It's 10 EUR for EuroStar Italia trains.