Always with the Kumhos and/or rim changes, upsizing rims, etc......it never ceases to amaze me how quick folks are to spend other people's money!
To O.P.:
You don't say how old the tires are that you're replacing, or if you've had any problems with them. If it's just time to replace and they've served you well, why not just replace in-kind?
Per Discount tires and Carlyles:
Isn't their guarantee enough to take them at their word? And I think you can buy extra coverage if you think you need it...though since you live in Les Schwab Country, I don't see why you wouldn't deal with them. We have for years, and most of our trailers are/have been equipment/cargo-type. We've had no problems with their house-brand ST's, which are built to Schwab specs.