phila to venice to amalfi coast or...

It works. US Airways has a non stop to Venice in summer, so it would be perfect if you can take that one. Otherwise you have non stops to VCE with Delta from JFK and ATL. Of course there are plenty of other choices through many big European hubs. Vueling as one daily flight from Naples to Barcelona in the afternoon, therefore it's the quickest choice from the Amalfi Coast to BCN. If that option is not available because sold out, you always have the choice to train back to Rome and taking one of the many flights from Rome to Barcelona. But if you can secure two seats on the Vueling from NAP, you'll save time and probably money.

You'd do better to fly Philly to Rome nonstop on U.S. Air and take a train down to Naples and the Amalfi Coast. Then take a train thru Rome up to Florence. You can take a 1 hr. bus ride down to Siena for a day trip. Then, it's a quick 150 mile train trip into Venice. Why not take the time you have allotted for Barcelona and spend it in Rome?
Then fly home from Venice on U.S. Air non stop. Barcelona is almost 800 miles from Venice, but can be reached by 2 budget airlines from Venice. I'd just hate to see you miss so much to see in Rome and its suburbs. Spain is a very large country, and a whole trip to itself.

Thanks for the prompt responses. I have to laugh, because we are trying to "wean" ourselves off Italy and finding it sooo... hard to do. That's why I really wanted to do Barcelona first (and we are spending 4 days in Barcelona area only...Spain is definitely a whole other trip)but no direct flights from Naples home. Thus the original question: Venice first or last? We have spent time in Rome and look forward to a return, but RT Rome vs flying open jaw didn't seem to make much difference in airfare and it seemed simpler/less train expense to take a more circular route. I love to be proven wrong! Talk to me.

Am sure you will get many responses but I think it would save time which on vacation is precious so would fly into one place, say Barcelona and then home from Rome. Have you checked other places you can fly from, say Newark for airfares?

To answer your last question, I would do Venice first. It is a wonderful city in which to recover from jetlag, as you have to walk (or boat) everywhere and there are no cars/scooters/bicycles. Also, the flights from Venice back to the US often leave brutally early. I agree with seeing Siena as a day trip by bus from Florence. Then train from Florence to either Naples or Salerno and then ferry/bus to your destination on the Amalfi Coast. You can then fly from Naples to Barcelona. I understand about trying to ween yourself off of Italy - I have been unsuccessful in my attempts so far (but I haven't really tried that hard)! :-)

Thanks for your input. I believe I am happy with the flight plans as I presented them, with a day trip to Siena from Florence. Is it advisable to book the Vueling flight (Naples to Barcelona) this far in advance? With the air booked I can begin the fun part...more questions to come.