I wouldn't go with any of the military replicas you mentioned. They're heavy, there aren't very many really good projectiles available, you'll definitely have to cast your own, and they'll generate enough recoil to the point that they won't be comfortable to shoot during an extended range session.
For traditionally-styled muzzleloaders, T/C is king here. They've taken all of the best features of original guns and combined them with the best modern necessities.
Definitely go with a gun capable of shooting conicals. Roundballs are great at the range, but they don't deliver enough downrange energy to be consistently effective. I don't care what anyone says about roundballs, THEY SUCK ON DEER and I sure as hell wouldn't use one on elk.
T/C's Renegade hunter would be my choice. It features a 1 in 48" twist, making it suitable for round ball or conical, it has a recoil pad, and is compact and light enough to carry through the woods after deer. I have a similar rifle, a left-handed Fox Ridge Outfitters rifle, which is more or less a Renegade from T/C's custom shop.
The T/C Renegade Hunter:
.50 caliber conical guns offer a good choice of projectiles. You can cast or buy ready-made slugs just about anywhere (it's like having a .30-06).