I might have to look into the HE-4... If I need rumble like that, I can always switch to my D2k with deep Cocobolo Rosewood cups.. Once cCasper TFG finishes recabling em and ships em to me. I can't wait to get those in my hands! But the HE-4 sounds promising and I DO want a planar open back can. The HE-500 was an all around disappointment for me..
Check out the HE 4 vs HE 500 and HE 400 threads, ideally the HE 4 is the DT 880 with the addition of linear Bass Response and an overall more tactile sound.