[NA Blur]

The answer is none.  Your solution to your bassless listening woes?  Denon AH-D2000.  Colorful with plenty of bass.  With an amp these sound amazing.  They are in the "Top Ten" headphones at headphone.com.  I really like mine.
 
http://www.headphone.com/headphones/denon-ah-d2000.php

 

[Chris_Himself]

Short answer: a good amount.
 
E9 will do just fine for it, probably should look into getting an M-Stage or HDP or one of the other beastly bang for the buck powerhouses for maximum listening pleasure a while later down the line