The EL-8 has a sensitivity of 102 db/mw, and a resistance of 30 ohms. The LCD-X has a sensitivity of 103 db/mw and 20 ohms.
So yes, you're right. It's a small difference though, as both are very, very easy to drive.
I think you're thinking of the Audeze Z or whatever with like 120 ohm resistance or something.
120 would actually be reasonable. The Z prototype reportedly had a 1200 ohm impedance!
http://www.innerfidelity.com/content/canjam-rmaf-2014-audeze-prototype-z-high-impedance-planar-magnetic-headphone