FWIW--
I recently replaced my 17.5 Coopers with Sailun S637. Have about 4500 miles, no problems, but still to early to tell if I made a good decision. I bought them on eBay for $175ea shipped to my house. $15ea for mounting. Have yet to hear any bad reports on them, but they are a Chinese brand.
My first set of Michelins lasted 4 years, looked like new, 2 had tread separations. Replaced with Cooper RM160s, lasted 3 years but I had axle problems that wore them badly. The Coopers were $264ea, and made the 15000 mile trip to Alaska just fine.
If you can afford them, Michelins should be a great choice.
If you want to check tire set pricing, check out:
www.trailertiresandwheels.com they know their business very well and ship anywhere.
Joe