USAirways has a fare of $107 (a bit over $200 with tax) from Seattle to Rome with a connection in Philadelphia. Naples and Florence price the same way (with a likely connection in Munich).
Lots of availability as it’s a coach ticket booked in H inventory, one of the higher coach classes.
You cannot depart after March 31st, there’s a six day minimum stay, you must travel on the weekend, and you cannot travel during the Christmas holidays
I’m able to get this to come up on Expedia, Orbitz, AA.com, and United.com. Sometimes I can get it on USAirways.com, but their website is glitchy.
Use a multi-city search and enter Seattle-Philadelphia, Philadelphia-Rome, Rome-Philadelpha, Philadelphia-Seattle.
Since this has been available since yesterday, I wouldn’t expect it to be up for much longer.