Haha you have basically named my entire collection of headphones. I currently have LCD2C (used to own LCD-2F), Atticus (have had 2 of them now), Auteur (have had 2 of them now), HD6XX (used to own HD650), Focal Elear (also own Elex), HD800 SDR, and TH-X00 (also EMU Teak). Eikon is the only one that I haven't owned, but I have auditioned on a number of occasions now. I feel the exact same about LCD2C as I can never get over the lack of slam and the upper mid dip. I was hoping LCD2C would fix that from LCD-2F but it didn't. I do have Mobius on the way so I'm still giving Audeze another chance. When I had LCD-2F at that time HD650 was my favorite headphone as well. Since LCD-2F couldn't cut it, I got rid of it and got my first cherry Atticus. Coincidentally, the guy I got my LCD-2F from had upgraded from LCD-2F to Atticus. And then the guy that I sold the LCD-2F to moved on after a few months and upgraded to his own Atticus as well. So there are definitely many people that have moved from LCD-2F to Atticus. I got rid of my cherry Atticus and replaced it with a Cocobolo Atticus and couldn't be happier. In short, Atticus to me is a super HD650 with bass boost. Same type of mids, same type of gentle treble, but a ton more mid-bass and better sub-bass extension. It is like a guilty pleasure HD650 when you crank up the bass EQ and just jam out. Yet it manages to have a wider soundstage, is more detailed, and responds just as well to source gear and tube amps in particular.
Now Eikon could also work for you too if you want more sub-bass rumble and less mid-bass slam. But if you don't need closed back than Auteur brings that same type of Eikon sound signature. It just depends on what type of "bigger bass slam" you want. I will say Elex completely fixes Elear's wonky mids so if that was the perfect headphone for you but the mids were the dealbreaker, well Elex does the job. Atticus slams harder in mid-bass than Elear/Elex, but Elex is all around a more dynamic/punchy presentation. Atticus mids are still more forward and lush like HD650 compared to Elex mids.
I have heard AFC on a couple occasions and I can't get into it. There was a
reddit thread a couple days ago that sparked a bit of controversy regarding AFC and how it lacks dynamics and feels a bit dead sounding. I completely agree with that view. I respect the design and comfort as well as the spot on tonal balance. But I just never enjoy listening to it. If you are looking for a closed back to replace AFC that is anything but lifeless, Atticus is it. Just know it won't be anywhere close to neutral and has its own character.