I've sampled around Kenya, sumatra, ethiopia, hawaii, vietnam, costa rica, columbia, yemen, jamaica and a dozen others. My favorites are from the Indonesian Islands especially Sumatra. I buy green beans from there in twenty pound lots at 5 to 6 dollars a pound.
I roast, outgas and grind it myself. My roasted is never more that five days old.
The very best that I've tasted is Kopi Luwak but I only have 361 grams of that left. That sells for $400 a pound roasted. And the USA allotment is only fifty pounds per year.
By the way, never buy a blend. A blend can be as little as ten percent of the named component. For instance, the James Bond favorite Jamaican Blue mountain sells for forty dollars a pound of green beans. A Jamaican Blue Mountain 'blend' which may be only ten percent of blue mountain beans, is also forty dollars a pound.
The University of southern Florida recently published a medical study that caffeinated coffee when fed to mice with Alzheimer showed that it slowed and prevented the disease. They did not use instant coffee in the study.