I had the same problem before watching Barakamon. Saw Handa-kun without realizing it was a prequel and didn't really like it. But I would absolutely second the recommendation to watch Barakamon!
Honestly, I watched Barakamon, and have really (like, *really*) liked it. I was thinking a lot about watching Handa-kun, but every time I read the summary, I get this feeling it has a *completely different* vibe :/