5 nighs for Seville and Barcelona.

Michael

I would say you have it right. Have you allowed a travel day for this? Are you flying or going by train?
Flying obviously would save time.
A lot to see in Barcelona- certainly Gaudi Architecture and Church - back street exploring, Rambles and the waterfront area.
Seville has an old Barrio which is interesting, as well as the Worlds fair area ,bullfights etc.
Both have their uniqueness.
Enjoy.

I agree with Shelly that 3 nights in BCN and 2 in SVQ is probably the best distribution of time. I disagree, however, with her statement that flying will save time. As things currently stand, between the hassle of getting out to the airport, going through security, waiting for baggage and getting from the airport to the city on the other end, it seems that taking the AVE (high speed train) directly from one city center to the other will actually save a couple of hours.

Here's my two day recommendation for Barcelona: http://quia-absurdum.com/barcelona/two_days.html

Have a great trip.

Michael

Im planning a trip too, this is my schedule so far for 3 days in Barcelona:
1 day Ramblas, Picaso museum and something more depending on the time.
1 day Everything from Gaudi
1 day Montjuic

Hope it helps