Quoted:
why is KAC discontinuing the legacy? Something wrong with it?
No, they are just using the newer URX 3.1 rail vs the URX II. The integrated front sight of the URX II wasnt well received by many of the .gov agency's KAC targets their products at, the result seems to be spilling over to the civilian products.
I bought a taupe legacy model in May from grabagun for about $1800 to my door. I sold the SOPMOD, rail covers, and vert grip for $300 so it netted down to $1500 for me.
As far as it being worth the extra $ vs. a 6920; I bought the SR-15 to replace a Colt. It started out as a 6520 lower with a 14.5" M4 upper and later I sold the Colt lower for a KAC lower. I bought the SR-15 lower first after handling the 14.5" SR-15 at the SHOT show, I planed to buy the upper when it was available and pin a FH. Once the 14.5" was for sale I realized the price for the upper wasn't far off what I could get a whole taupe gun for. After buying the SR-15 I've never looked back,
to me it's worth twice the price of a 6920, maybe more.
If you haven't had the chance to shoot a SR-15, do it. Even handling the rifle was enough to make up my mind. It seems like its a case of "more than the sum of its parts", you can look at the spec sheet for the SR-15 but it just doesn't convey how light, balanced, quick handling, and soft shooting it is.