Not an LCD owner but prior to getting my T50RP 50th Anni (which now does most of the heavy lifting for any bassier music) whenever I wanted to listen to my K702 over my other cans but wanted to enjoy some nice bass I would just stick a stupid +12-15dB bass shelf on there similar to yours and call it a day. It surprisingly took it like a champ.
I haven't yet tried doing the same on the planar goodness that is the T50RP 50th Anni, but I may do later today when I have a moment to listen, just for the hell of seeing what these drivers can actually handle.
To be honest unless I'm missing something (I'm less familiar with the other models in the MDR series you listed), that entire list is side-grades or down-grades*, so I'm not particularly surprised you still like them best.
(*By down-grades I don't mean objectively worse in every sense, I mean a headphone that falls into a lower performance tier than yours, and by side-grades I mean headphones that fall into a similar performance tier)
Even when you upgrade to a higher performance tier with headphones there's often trade-offs.
Since just about every other variable of headphone qualities can eventually be summed to frequency response at the ear canal, that means it doesn't matter if you're improving the bass, fixing weird treble, making a headphone sound "faster" or more detailed, you are at the end of the day ending up with anywhere from a slightly different, to very different final frequency response. That in turn reflects back onto all those other individual variables: That improved bass might mean maybe those mids don't cut through the mix quite so nicely as before. That "fast and tight" bass might mean the overall quantity of bass is a bit lower. That increased detail, might mean a brighter and more fatiguing signature that isn't as easy listening to for long hours.
So almost every switch from one headphone to another, even when jumping up price changes means "You get this, but.." and it's just a question of finding a "but" that doesn't bother you. Sometimes the "but" is a pure improvement, like the tuning being radically different but sounding better in every way, but you won't find two headphones that are identical carbon copies of each other with one simply being identical but better, there's always going to be something different about the sound and that often means some kind of trade-off.
It actually feels really special when you do find a pair of headphones that's just an overall improvement in all the areas you liked the original pair for, rather than an upgrade in 2/3 and a down-grade in the other 1/3.