What month?
It's pretty wide open, and I don't think you can really go wrong, so I'll just throw out some considerations. Scandinavia would be vastly more expensive than all of the others.
For Turkey and Greece, I think 10 days is the bare minimum (especially if you are not coming from the east coast) because it is just so hard to narrow down form the many attractions. With a well-edited itinerary, you could certainly put together a nice trip, but I'd be more comfortable with closer to 2 full weeks.
Could you elaborate on what you liked about Hungary?
You might consider Slovakia--I have not been there, but met some fellow travelers who raved about its castles. Slovakia and Poland might make a nice trip.
Lots of Croatia (and Slovenia) fans here, so if you decide on that you'll get great advice.

Probably looking some time around August. We usually go in the Fall, but due to kids' school we are probably going to have to go end of summer this year.

I've looked at Turkey/Greece options and tend to agree - too much transport time to do both. If had to choose leaning Turkey. Obviously its going to be hot there in August, so thats a consideration.

Hard to really describe, but Hungary (Budapest) just had that "it factor" for us. Enjoyed the food, architecture, both ancient and modern historical sights (communism/nazi control). It is an up and coming country - so its modern but still with some work to do/rough edges. Unlike, for example, Vienna which is very refined/higher end. We really just enjoyed being part of that emerging culture where things are starting to thrive.

I loved Budapest also, and I think that will help others give advice.
I even meant too little time to either Turkey or Greece, but I am a hypocrite because I did do about 10 days in Turkey, and it was one of my best trips, but it is really really hard to narrow down. (I chose Istanbul and Cappadocia.)
If I had to travel in summer, I'd either splash out on Scandinavia (if only--ha!) or strongly consider Poland. As much as I love Croatia, it can be very crowded on the coast in summer (unless you want a truly off the beaten path of inland Croatia--more of a nature trip for the northern/eastern national parks, but there are castles around Zagreb as well).
There's also Bosnia. Tough decision!

Appreciate your feedback yorkshire!

The most critical factor you mentioned was the month---August.
Most Europeans vacation then and the popular resort aresa are wall to wall. Italy, Greece, and most of Spain are too hot in August. If that month is locked in then I suggest Ireland or the Salzkammergut region of Austria.

We loved Budapest too for the same reasons you did. Have you thought about Russia?

Don't give up on Scandinavia too quickly. We are going to Sweden, Norway and Iceland in August. We are fine with hostels so accomodation for the five of us is not much more than what couples pay for a hotel room.

But what really makes it affordable is the airfare. Toronto-Stockholm and then Stavanger-Reykjavik-Toronto for $990 on Icelandair. That will help offset the price of gas. I doubt anything will offset the price of food.

> We're currently considering Scandinavia (Copenhagen, Stockholm, Oslo), Turkey and possibly Greece. I've also seen some amazing pictures of Slovenia and Croatia, so those are also of interest. We also considered Poland as part of our last trip but didn't have the time.

I've been to all of these except Oslo and Greece and can say that you'll see some wonderful things no matter what you choose!

As others have noted, Scandinavia will be the most expensive, but oh my, it is beautiful! And 10 days would. IMHO, make for a very pleasant visit.

I could easily be wrong, but I would think that Turkey and Greece would be hot. Too, you'd have to be quite selective - I couldn't figure out how to spend less than 25 days in just western Turkey!

And I loved Slovenia and Croatia, but they didn't jump to my mind when you described why you loved France and Hungary; I'm not sure why. It's not that they don't have the things you mention - they do! Depending on where you were to go exactly, crowds could be a problem at that time of year.

In Poland, I loved Krakow and was glad I had the chance to visit Warsaw, though I must admit that it didn't win my heart the way other places have. I have not had the chance to visit other parts of Poland.

Hope this helps!