I'm in the same market. I have the national standard duty, and they have served me well. I have out grown them and need some HDs.
I'm considering both WSI and the Nationals through RPG. From what I'm learning, the WSI pack is pretty strong, meaning you will need weight in your bed when going off road. But towing will be no problem. Also they are probably arched a bit more than the Nationals. Both have good bushings.
If you're just looking for towing capacity, you could go with the add-a-leaf option. This would be your cheapest option.
Lastly, I think sdhq offers bags.
Yukon Joe
Buffalo Run Support Raptor
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