If you really want bass and clarity, you're talking mostly about the Fostex TH900/TH600.
The Audio Technica WS99 is a good option as well, but it is probably a slight downgrade from the M100.
I'm not aware of any other full-size headphones that give you extreme basshead-level bass in addition to excellent clarity and soundstage other than the Fostex TH900/600 or the Denons they (Foster Electronics) made previously (D5000 and D7000 in particular).
The SZ1000/SZ2000 have tremendous bass impact, but honestly the clarity is where they suffer. I want another pair after I sold mine off, but that's exclusively for the insane impact, not for the clarity.
It's the same dream I've been chasing, and I found it in the Fostex TH600. I need to temporarily sell off either those or the JVC HP-DX1000 (also amazing, but not as much separation or clarity as the TH600--better in some other ways though), but I'll get them or the TH900 again at some point if I manage to sell them.
Thank you very much for this insight !! I've looked at the TH600 and a bit con for me is the SPL max.: 94 dB / mW. This is pretty low...