The Encore's a good platform. I don't know whether they offer muzzleloader barrels with a quick-release breech plug, but as long as you take care of it you probably won't have much trouble removing a regular Encore muzzleloader barrel's plug.
On the subject of Mike Bellm, if you're willing to purchase the inexpensive parts and spend time installing them, and especially if you'll be shooting it at longer ranges, duos should efinitely make the investment. I personally recommend one of his lighter trigger springs.