With out a doubt it would have to be Africa for Cape Buffalo, preferably charging, with a muzzle loader of course. ( I know, what is a Cape Buff doing charging with a muzzle loader?)
Once there I would go for several species of plain game, antelope. I have no interest in shooting an elephant or a lion, but the Leopard is a real prize.
Really it isn't all that expensive. You can take five species of large antelope for about 6 grand, not including trophy fees and airfare.
If I remember right a Cape would set you back another 2500, so for less than 10 you could have the Africa hunt. A guided griz hunt in Alaska will cost about that much.
I do think tht I'd want a bullet shooter for buff, at least .45 with a 500 plus grain bullet at 1200 f.p.s or better.
Sounds like another custom rifle is in order for this one hey?