I used to own the HE-1000SE (HEK) and still own the HE-6SE (HE6). While I had them both, here are my findings in no particular order;
- HEK was more versatile and easier to drive
- HEK was slightly more comfortable because of the shape
- HE6 slammed harder when driven properly
- HE6 was more intimate vs HEK staging wise (even with the grill mod)
- HE6 and HEK both sound great out of the box but HE6 could be tweaked to slightly improve it while HEK didn't need to
- HEK is taller and wider but HE6 goes deeper
Note: My chain at the time was as follows:
DAC: Holo Audio May
Amp: Studio Six, La Figaro 339, Pathos InPol Ear, ECP DHSA 3F