The case really depends on what you want from it. I recently picked up a Silverstone Grandia GD07, and it's great! I really like a clean look, so thats why i picked it over a case which has the 5.25 inch bays exposed.
About the cpu, it good enough for League, and you could try and unlock the 3rd and 4th core. I have done this with my Phenom II 560 and it worked great! Altough keep in mind that yours might have a damaged 3rd or 4th core, so it has been rebranded as a 555.