Christian,
It all depends on you. I have a bachelors in finance, and studied maybe 125 hours total...with 90 of those hours coming in the last 9 days prior to the exam. I solely used the CFA books, and took their practice exams. (I passed)
I would not recommend that though. Going into level 2, i plan on studying way more.
Stala, schweser, qbank....if you feel like you need extra help, I think I would go for it, but the books are definitely sufficient enough to pass, as long as you understand what you are reading. I thought they did a good job in explaining things.