DO NOT, I repeat DO NOT buy from BFL . Liars , cheaters , scammers.

KnC look good also http://cointerra.com/ look solid. Do your math right, difficulty is going up fast. You may not even make your money back.

https://en.bitcoin.it/wiki/Mining_hardware_comparison

Always do your math and research before investing your money. If you wanna do it for fun you can always get a Jalapeno or even mine with your smartphone.