I use the Kimpex on my Rincon and like it a lot. I also have one on my Grizzly.
My only complaint is that the Rincon's rear rack isn't very deep, so the box hangs off the back 4-5". I attach the box using U-bolts so it stays in place, and I also added my own weathestripping to keep the dust and moisture out.
This is the only box I've found with metal, locking latches. You can even buy replacement latches ($10 each) if they happen to break. It takes a lot to break them. The one on the Rincon is the one that came off of my Arctic Cat 400, which I rolled down a very steep hill about a year ago. The box was flattened out and the latches ripped off. Rather than throw it away, I tossed it in the back yard and ignored it for a few months.
Then one day I was out there and about to toss it, when I noticed that it had returned it its original shape. Wow. So I called up Kimpex, got the part numbers, and ordered new latches from the dealer I got it from (ATV Direct). A few weeks later, the latches arrived. I removed the remains of the old latches and attached the new ones with nuts and bolts, and it's been working great ever since.
The only box that could be a better fit is a really nice heavy duty box from Polaris. It's not as deep, but it's an inch taller. It has rubber latches that aren't locking, but it's a double-wall box with a really nice weather seal. It only says Polaris on top so it wouldn't be so obvious to bystanders.
Rob