Bass quantity is all relative. For people who prefer a neutral signature the HP50 has plenty of bass. You might want to try it first because I found it uncomfortable. I don't know what they were smoking when they designed that headband.
For reference I use a Q701 with the bass mod and think it's just right. More bass isn't bad, but I don't want my bass walking over the mids or losing detail. I prefer less bass that's better than more that's bad.
HD25 ALU, VK-1, Q40, even the HD650 but it's not a relevant comparison. I felt that it had similar bass quantity to the K550 and that's known for having little bass.
K545 is one of the ones on my list too, which is supposed to have more bass than the 550. You're saying the HP50 has less bass than that? That's not what I read in the K545 thread...