That was going to be my comment. SCI is not many months away and should allow you to look at and handle many different double rifles and calibres in the one place.

There is a Californian Side by Side Society or some name like that, but I do not know much about them except they thought I should pay THEM advertising dollars to do a simple link exchange. They have a web site. They MAY have events which you could attend and look at some of the owners personal double rifles.

I too would vote personally for a .500 NE if the choice was between .577 and .500). Check out 500grains elephant hunt report on the Hunt Reports forum where he used his Searcy .500 NE on several elephant and buffalo.

Otherwise I would also consider out of the following: .450/.400; .500/.416; .450; .470.