I would check out Crane toilets.
During the greater NYC toilet change out we installed several thouand toilets ALL gravity drainage Crane with not one single call back.
The Kohler I cannot say the same about as I had several problems with them and American Standard.
Gerber is also a decent toilet if Crane is not available.
Unfortuntly a lot of these manufacturers are having these products made in other coutries where the quality control is IMHO VERY questionable to say the very least.
Try to stick with Gravity type not pressure assisted Good Luck.