Dude,
You are going to have a very tough time finding an aftermarket rear bumper that is not custom made and will let you keep your standard class III tow hitch. The mounting points for the tow hitch are almost always used for the new bumper. Also since there are so many different designs of hitches, it is almost impossible to build a bolt on replacement off-road bumper that guarantees fit.
Most of the after market bumpers like Demello, etc are rated for off-road towing only. This is for legal reasons, not strength. It costs a lof of money for a shop to be licenced to sell products with a tow rating.
There is some talk that Asfir bumpers (from Israel) may be able to accomidate the stock trailer htich, but I haven't heard of any of their product actually making it to North America and being put for sale.
To add to your list of bumper companies, try
www.sonoransteel.com. They make a nice product. Demello is also a top choice.
Pete