I'd put the 499 ohms on it and see how it sounds. If the highs seem rolled off then go a little higher, but you may find that the 499 works just fine. I have the Ebony L, which is a little lower output. It seems to like 280 ohms or thereabouts, in my system.
Benz Ebony LP loading
Has anyone experimented with the loading of the LP? It says greater than 500 ohm. The Ayre K1xe can do 499 ohms, but I'm thinking that may be too tight. Has anyone done any experimenting??