First let me say that I used the foams supplied with the Temperament X6 on both LLBS and X6 for my listening comparisons. That is one less variable to throw off any impressions.I have read that but for someone who already have Ks LBBS is it worth it to get the X6 in your opinion? Is the noticable difference only in the bass? How about the feeling of grandness or the illusion of soundstage?
The 2 sets have similar traits (timbre and technicalities (aka, house sound)), but they also differ from each other as well. To my ears, LBBS has a mid-bass / mid-range / treble focus. Because of that, there's good instrument separation and some sparkle is prevalent. The X6 (Temperament) has a richer, fuller sound because of bass presence while not losing much in the mids and treble compared to LBBS. While the X6 may not have as good of instrument separation as the LBBS and the sparkle is a little subdued (but still present) due to the bass, their sound has a better overall balance.
Grandness goes to the X6 (due to better bass for a richer, fuller sound)
Soundstage is similar, but instrument separation stands out more on the LBBS (due to mids / treble focus).
Temperament is labeling the X6 as "Model BELL-LBS" on the box, so you would think they would be tuned to sound the same as the LBS / LBBS, but from what I'm hearing they are not tuned the same. I actually like both of them for their differences and I already mentioned that I'll most likely get a set of the Temperament X3 (Onmyoji version) during the next major AE sale.
Hope that helps.