Rukus,
Welcome to the best forum.
There are some excellent Safari Companies and PHs participating in this forum.
Do not hesitate to ask them very pointed questions about buffalo hunting, as well as hunting and fishing in general, as it pertains to Africa.
They are a wealth of information because most if not all of them were born and raised in bush or at least rural Africa, with a rifle in one hand and a fishing rod in the other.
Regarding double rifles, I think the Searcy ones are a good buy, as are Verney-Carron, Chapuis and Heym.
Once I bought a brand new Merkel (.375 H&H) and it was shootable/accurate but, the right side chamber was too tight, causing primers to flatten and sticky extraction, with the factory ammunition it was supposedly regulated for.
Furthermore, I prefer doubles to have approximately 26" barrels, as they seem to balance better for me.
The Merkels all seem to have 23.something inch barrels - too short for my taste.
My personal preference for current day/new made doubles (that a working person can actually afford) is the Heym PH Model.
I have a Heym 88B (mechanically about the same rifle as the PH Model, only cosmetically different) that I bought used but in like new condition, and so far I am very happy with it (in spite of the fact that Cal Pappas makes fun of it for not being a London or Birmingham built rifle).
It balances well for me (25.5" ejector barrels) and regulates quite well indeed.
At 9.9 pound, it has a hefty recoil (it's a .458 Winchester) but it regulates so well with 500 grain bullets that I am willing to put up with being punched around a bit from it.
Nonetheless, when you get a chance, have a peep at:
www.calpappas.com
Cal is rapidly becoming one of the world's authorities on particularly English double rifles but, also somewhat on double rifles in general.
Cheers,
Velo Dog.