A friend of mine has the Dr mower. I've seen it in action, it runs through everything. He swears by it.
He has the snow thrower attachment for it.
He wants to get their chipper next to replace his old Tomahawk.

The DR does have a good reputation. I know Billygoat makes one too and I have read good about it too. I don't know the price but you might want to give it a look. How often are you going to use it? Maybe renting one would be better or you could look for an old Gravely. They can be had cheap and their absolute tanks. - Kris

I purchased the commercial DR Field and Brush Mower last year. The price was kinda steep, but it does everything it's advertised to do. I'm very satisfied with it.

We bought the DR 12.5Hp electric start model when it first came out, worked it pretty hard at first clearing some overgrown land. The machine does pretty much everything DR says it will, but reliability was a problem. Think they have fixed many of the problems in later models, and we have received a number of upgrade kits from DR over the years. Principal weakness is that the underside of the machine (where the wheel drive belt and chain are located) is open, and if a stick pops up in the wrong area it either flips the wheel drive V-belt (mower won't go out of gear) or breaks the chain (have to drag the dang thing back to where you can replace the chain). Hazel nut bushes are the worst, the stalks are tough and tend to spring back up under the machine and cause havoc. Machine eats black berry bushes and 6' tall Johnson grass like its going out of style.