Slavic languages, which group to go after?

Ok /lang/, I'm learning German and want to learn a slavic language, question is, which one?

I know the basics about slavic languages, bulgarian and macedonian are intelligible, croatian/serbian/bosnian are nearly identical, with some basic differences, and czech and slovak are intelligible.

I know that the obvious choice is Russian due to the home country's affluence in the world, but everyone learns Russian.
Poland doesn't suck too badly, but could be better, so its language isn't a terrible choice.

Which one would I learn to get the most in-the-middle language, so that if I wanted to, learning the other ones would be easier than say learning Czech, then trying to learn Bulgarian?

I want to learn one because I enjoy the way they sound, I just don't know which one to learn.

Learn Czech.

1. The Czech Republic isn't a medieval, xenophobic, genocidal conservative Christian hellhole (lol Serbia)

2. The Czech Republic has a working economic model and a very high standard of living (its HDI is 0.903, making it 36th in the world, and the highest of all Slav countries), unlike some other countries (lol Russia)

3. The Czech Republic has a decent reputation (unlike Poland)

4. It is beautiful and historic (unlike the Ukraine)

5. It is in a great location in the middle of Old Europe (unlike, say, Bulgaria (enjoy your Turks!))