what is a good site to upgrade in?

It really depends on what sites you're a part of. The best thing to do would be to look at all the sites you're a part of and see what the cost and perks of upgrading are of each. Then, compare them side by side and note the pros and cons of each. Also, ask upgraded members of the same site what they think of upgrading if you can. Be sure to take into account whether the fact that you're in the Netherlands will have an effect.

I have to say that I do not know the answer to this. What sites are you currently using? That might help.