From my experience so far, I wouldn't bother changing out barrels. I upgraded my Smooth Twist Impact to the X Barrel. Not enough difference to warrant the change. I am sure that someone with the proper tooling could make the change, but the accuracy difference doesn't seem to be enough to do the deed.
I'm also waiting for the Dreamline, but we'll see how it goes. Originally, I understood that pre-orders for the first gen dreamlines was supposed to be happening now, but FX is late on that one. Maybe after the first of the year?