Have you tried using ebay or searchtempest.com to find a terramite? I found mine on ebay. Drove 300 miles to get it. I'll never be without it. Just wish I could play with it every day.
I also found a 10k dump trailer on ebay. Picked it up in Elkart, In. 200 mile trip for me.
I recently purchased a 2012 Kawasaki mule 4010. Don't really need it, but the grandkids like it. I've been using the terramite to make more trails in my old gravel pit to drive the mule on. Having fun making trails and having fun giving the grandkids a ride on the mule.
As for your trailer. The most I carry is 5k. I wish my trailer was a 10k, because it would be a few hundred pounds lighter, so I could add those few pounds to the trailer. 10k is all my 1500 truck likes to pull.
Want to buy a 14K? When I pull the 14k without a load, it bounces like a basket ball. The tires are inflated to 90 psi. Put a 3k terramite on it and there is a world of difference in the ride. Also, a 10k will have smaller tires, cheaper, and the deck will be closer to the ground. Less of an incline to climb.
BYW, I asked the same question you did on YT. Most replies on here were, you never know when you might need it, go big. Well, I'll never damage my 14k, but definately wished I had a 10k instead. I upgraded from a 7k, which I sometimes bent the front axle.