Yes, I have a .177 hw barrel on my xs20. The only thing I had to do was shim the breech seal up 0.5mm as the lock up didn't put sufficient pressure on the seal.
You can also , with a minor mod fit a rekord trigger blade to the rekord copy trigger. I would say don't rush out and buy a new xs20 but go for the older cloned 95 as they changed the trigger on later rifles