They’re certainly good cans, I’ve seen it said that they were even the best money could buy when they were released in 2003 although in a hobby as subjective as this I find that to be a dubious claim.

I highly suspect the headphones are fine and your brain is just getting used to the different sound. I thought my HD6XX were crap (edit; actually, just very ‘samey’ compared to my other cans at the time) initially, now they are like nothing I have ever experienced anywhere else; literal velvet sound.

My X2’s have decent bass but it’s not in ‘blow me away’ territory, just a bit of a bump. As others have remarked my treble is also quite grainy compared to my other cans and that may or may not be for you; once I heard it I could never not hear it again.

I’ve never tried the Superlux so I can’t compare to those.

HD598, with my HD6XX being a runner up even though many people have a hell of a hard time getting them comfy for their use.

Stupid but not really that stupid :^)

They’re good headphones, I had the XM2; I liked them while they lasted but after 2 weeks or so they stopped working and they didn’t have any to replace them so I refunded them.

The noise cancelling is a real boon imo, you just don’t hear things like engines with them on.