I know it's a bit late, but I second the recommendation of the Brown Cutters.
It's been mentioned that they are some of the most heavy duty cutters you can buy and that is true. In fact, they're 600 series 5' cutter would be too much for your tractor so quite honestly, you wouldn't be able to handle the heaviest ones they make.
Also, I believe all the major players are using Chinese gearboxes now-Woods, Landpride, Bush Hog etc. Brown uses American made gear boxes in their 600 series mowers (but not in the 400 series).
The Woods cutter you purchased will make an excellent cutter for almost anyone's needs. I imagine it will outlive you.
Congrats, I've never heard anyone complaining about getting a too heavy duty cutter.