We have cruised 13 times on Carnival, RCCL and NCL, and of course Costa. To be blunt, we were on one of Costa's newer ships, identical to Carnival's Conquest class ships and it was a 7 Day Med. and our only regret was that we didn't book with a more mainstream Cruiseline like Carnival, NCL or RCCL. HAL or Princess would have been fine as well.
The food was inferior to any other cruise experience we had ever had. The service in the dining rooms and food quality was inferior. Staff were sometimes openly antagonistic to passengers. Certain cultural differences created issues, such as the French and Italians desire to cut in line, and not allow people to exit elevators, pushing the door close button to prevent people from getting on to the elevator.
If it was my 25th Anniversary and I was paying for airfare and all the other expense that goes along with a trip of this magnitude, I would pay extra on a better line than Costa. There are major bargains to be had right now.
I just got a flyer from my travel agent, offering 2 for 1 cruise fair on a 7 day Med Cruise on Luxury Line Regent Seven Seas, which was around $3700 and included free air. This did not include taxes of $400 pp, but it is an all inclusive line, includes alcohol, all meals onboard, free shore excursions, and gratuities, oh yes in a suite. It was in October, so would not work for your purposes, but my point is, there are great deals out there. It may not be necessary to compromise quality for price right now. Also, you may know this, but make sure you pack appropriately for February in the Med. It can be quite chilly and seas can be a bit rough. We were there in November and aside from the Thalassotherapy pool in the spa, we never went in the pool as it was pretty cold.
If you do decide to book Costa, and you enjoy wine and beer with meals, you might consider the X1 Package. There is a another thread here that details the package.
Hope that helps.
I wish I had been a bit more selective when I booked our Med Cruise. But the Med is beautiful and I am glad we made it there regardless.