As others have noted what will be the primary use of the mixer?
When I was baking six loaves of whole wheat bread at a time i used a Bosch Universal and it handled that much dough with no problems at all. There are other comparable mixers that can also handle similar amounts of dough.
My baking has changed over the years so now I make much less bread and more stuff like cakes, cookies, whipping cream, making frostings, and such. To the end I bought a KitchenAid Pro 600.
While I can do these things in the Bosch it's design is not as convenient as the KA. While I can make bread using my KA it is not suited for making more than about two loaves of whole wheat bread at a time as that is not what it is designed for.
Generally speaking unless you're wanting to make more than two loaves of whole wheat (3 to 4 of straight white bread) at one time I would go with a KitchenAid model. My mother and grandmother had tilt head models, but I chose to go with a bowl lift for greater durability. I think the KA design is more all around versatile for a wide range of possible uses. If bread is your primary use then go with a Bosch or other similar design.