@Bellyworshipper : considering your "basshead" preference, either one would be fine. They both have an excellent bass quantity and quality, and will not limit the low end extension, both have a good control, L5P has a slightly better decay while N6 will be a little faster. But all this is irrelevant. Your need good basshead headphones, and I can re-assure you that neither N6 nor L5P will be a limiting factor to get that bass slam. My personal preference goes for L5P. N6 is great, but when you really compare one to the other, L5P sounds more analog, more musical, while N6 is more digital, a little sharper.
I'm, kind of, more on the basshead side that's why after reading some reviews on Cayin N6 (did not have an opportunity to audition it) I decided not to buy it, notwithstanding all its advantages. Now I'm curious about comparison of N6 and L5Pro lows performance...