Yes, the LCD-X is most certainly an upgrade from the EL-8 open. I just made this change to upgrade, selling both my EL-8 open and closed, and buying an LCD-X.
However, there are some complexities. I'm glad you mentioned specifically you are seeking to get rid of some of the dull nature of the EL-8. The 2015 original edition of the EL-8 was actually a little brighter, perhaps artificially so. That is the brightness was a little grating, and not necessarily clearer or of a higher resolution. I know because I sent my EL-8 closed in for the upgrade, after purchasing an EL-8 open of the 2016 variety. The 2016 became, in my opinion, easier to listen to - more relaxed sounding, and less harsh. But as you stated, there are details missing.
The 2016 version of the LCD-X has, in opposite to the EL-8, become more detailed. While the original 2013 version of the LCD-X was darker by comparison. So per your desire to upgrade and to gain a headphone that is less dull, I think the LCD-X is quite the right direction for you!
I've only limited experience with the LCD-3. Hmm...HD800S. That's a tough comparison, as I own it too! It depends on where you want the headphone to hit the hardest. Bass depth and impact, there's no comparison with the LCD-X. Spacial cues, the HD800S still does best. And, though I've limited experience with your Lyr 2 amplifier, I'm inclined to think it would be better for the LCD-X than it is for the HD800S. The Valhalla 2 is the natural pair for the HD800S. I owned that and it was fantastic, only selling because...well, upgrades happen. But the amplifier I upgraded to (initially) was three times the cost of the Valhalla 2. The Valhalla 2 is still in my opinion quite good with the HD800S.
