Where to go!?!
 

My wife and I are around 30. We love good food, good drink, art, quirky surprises, a little nightlife, and safety! Also, a good value is important, though not imperative.

We've been to these European cities:
London
Dublin
Paris
Munich
Barcelona
Prague
Amsterdam

We have about 10 days in May. Which two cities should we go to next (excluding Italy - we're going to do that another time). Thanks for your suggestions!

May is a nice time to visit the countryside. Have you considered combining a city with the countryside? You might enjoy the combination of Nice and the Luberon countryside.

<<Which two cities should we go to next (excluding Italy - we're going to do that another time)>>

There are quite a great few cities and regions in Italy to explore, so you might consider it. IMO it is impossible to visit Italy just once- you will want to return to Italy for more visits, guaranteed.

Madrid and Seville;

Big city art, small city quirkiness, amazing European art and fantastic Moorish architecture. The best food in Europe if you like extreme quality in simple presentation; cured and roasted meat, cheese, olives, etc. instead of creme of this, or avant garde that, and extremely fine underrated wine; Rioja's and Ribera de Duero's. Yes, yes, I know it is subjective.

Ribera del Duero's

Go to Croatia/Slovenia - I'm going (back) there at around the same time as you'd be there. Ten days there isn't a lot of time, though.

Budapest and Vienna.

I go along with Andrew's choices...although with only ten days, limit to Croatia. It's a good matchup of small cities, towns and villages, scenic, welcoming, good food choices. I started traveling in the area when Tito was in power. Later when the former Yugoslavia split into half a dozen countries, none of the attraction was lost. Neither will you need a second mortgage.

One other suggeston is Portugal, a most underrated destination. We loved it.