First start with a brand or two that you like. Read up lots of reviews on their prosummer models. You will find adherents to every brand, so that is somewhat meaningless. I have always liked Nikon, so some years ago I did the research and bought one of their mid priced models. I like it. But now I own several lenses, and they are where the money is. So I can't easily go look at Canon.
R
molṑn labe'
"I am a mortal enemy to arbitrary government and unlimited power. I am naturally very jealous for the rights and liberties of my country, and the least encroachment of those invaluable privileges is apt to make my blood boil."
--Ben Franklin