We too like Celebrity. and we took their 12 day Mediterranean cruise out of Rome in April to Malta, the Greek Isles, Turkey, Athens, & Crete--ending in Venice. The outside room price was right @ $1,233 per person including a $600 all you could drink package, all tips (room & dining) and a $75 credit for the shops. Any cheaper and they'd been paying us to go.
A year ago, we took a Baltic cruise from Copenhagen to all the Scandinavian countries and St. Petersburg, Russia with Norwegian Cruise Line. I suggest avoiding Norwegian as they're in transition after upper management changes. The food was terrible.
Both cruises were trips of a lifetime, as you can go a few days early and stay a few days after the trip's end.