For me, and endgame headphone needs to achieve two things: it needs to be balanced and natural enough to be enjoyable with a wide range of music (also very easy to tweak the rest of the chain) and it also needs to be magical (ipad jokes incoming). Some headphones do one thing well, HD600 comes to mind for the first, HE90 for the second.
Luckily, for me, the SR-Lambda scores a double hit.
After the first try in 2009, somehow along the way, I lost sight of how unremarkably amazing it was, but all is well since 2012. Flirting with other headphones is jolly good fun, in that sense, there is no endgame headphone. But in this case, it's only about keeping the relationship stable and everlasting 😏