With your desire to shoot roundball and concicals, I would suggest the barrel have a 1-48 twist. Because the rifle is so versitile, as far as additional barrels to change the rifle's characterstics down the road, I would suggest a .54 caliber Renegade or T/C Hawkins. Then if down the road you wanted a fast twist or a shotgun, a simple Green Mountain Barrel will have you doing all of that as well.

Watch the auction sites. Used ones show up on them and can be picked up reasonable.