HFI 580 and above
Pro line for sure. I listened to the 750s ages ago, and I remember them giving my DT770 a run for their money with the bass dept, with better portability/fold-able. I wouldn't mind grabbing them again.
Haven't heard any of the Performance line, but would pick one up to try, judging by the reviews.
I think the problem with this headphone (it seems great for the price) is that there's a lot of China brand/off brand alternatives compared to a few years ago, with (likely) a better sound to boot, if not the same (speculation on my part).