“I will be the first to agree that variables make a perfect data base impossible. I just find it very interesting to see how each combo performs. I guess the biggest single variable is the buffalo.” reflex264

I have watched some videos and wasn’t impressed with some of the shooting. Just remember they wouldn’t be as exciting to watch (or marketable) if the hunter drops the buff with the first shot or double taps it and it falls in a heap. I didn’t count how many head of game I saw drop with the first shot while walking the DSC show last month. nearly all the outfitters had videos running.
I think you have Ben given some good advise so far. I would recommend a new production rifle and have it ordered to fit you. Save the classic used English rifles till you have some experience with a double.
The 450/400 is going to be more popular now that ammo will be readily available. I would recommend the 470 caliber because of its easier to sell if you decide to upgrade. The same for a 9.3X74R this will give you a double you can shoot cheaply and kill everything. No it is not considered a “stopper” but it has been used successfully on everything.
Chapuis, Merkel, Krieghoff, Heym, Searcy are all makers you should look at.
I would try to go to one of the events where you can see and handle several makers rifles to get a better feel for what you like.
Bill