So ... has anyone had a chance to listen and compare all of these?
The samples I heard suggest that X3/Xt/2.0 used the same tone engine, and the HD is different.

And the same guitar amp has entirely different sound via HD as compared to earlier ones. They claim that HD is 100 times more accurate. Wonder where that leaves the older ones? Not close to the actual amps?
But the claims then were that Line 6 POD is the closest thing to the real amp.