Terrible flushing - Duravit Starck 2 Happy D
I do not know anything about your toilet, but I have 2 types in my house. I have 2 Kohler Cimarron 2 model K4421 which are great and a new American Standard  Champion 4 max just recently installed. The American Standard is supposed to be able to flush a bucket of golf balls. Don't tell my p..p that. It doesn't always go down completely. I would choose the Kohler. Also we use " never scrub " cartridges to help keep the bowl clean.