As the 670 is a huge! battleship I recommend a larger tower to get a better airflow. Also think about that cooling is very important these days. Better too much than too little. Buy more cooler
I also have this cheap little thingy under my 570
http://www.amazon.co.uk/Evercool-SB-F1- ... 745&sr=8-1
looks stupid but it somewhat cooler

