I bought and installed an AS Champion Round bowl toilet. This was in spite of the reviews in your page. This was also in spite of my neighbors experience with two AS Champions. Actually it was four AS Champions. About two years ago he installed one. Turned out it was leaking through the china to the outside of the bowl. Not at a seal, but actually through a hole/crack in the side of the bowl unit over the channel that pipes the water from the tank to the bowl. He returned it to Home Depot and got a second one that installed and worked without problems. He was happy with the unit and about nine months later, he installed a second AS Champion in their second bathroom. This one also leaked through the china (not at a seal) at the bottom of the same pipe from the tank to the bowl. Again, he returned it Home Depot, got another bowl and installed it with no further trouble. After all was said and done, he like the toilets. The clunk wasn't that intrusive and it had a powerful flush. Based on this, I bought an AS Champion from Home Depot as well.
I had the same problem he did. I even inspected the bowl unit in the store looking for voids in the bowl casting and saw none. It turns out there was a hairline crack in the pipe/channel from the tank to the bowl at the bottom of the bowl unit that I didn't see. It leaked about a table spoon or two with each flush. There was no water visible on the bathroom floor. I have an unfinished basement under the bathroom and a small puddle appeared in the basement the day the toilet was installed. At first I thought it was the wax ring, but remembered my neighbors leaks. I took the toilet outside, tilted it so the pipe (in the bowl unit) from the tank to the bowl would hold water after I poured water down the hole from the tank. I could see a drip a second coming from the crack, even though the crack was barely visible. I also returned the bowl to Home Depot. HD replace the bowl, no questions asked. I installed the replacement and have had no problems since.
The Quality Control seems to be pathetic based on these three units. But, the toilet can seriously move waste material and I'm getting used to the clunk. We'll see how well the valve/tower unit holds up.
Jon