Flushing out a problem

Allow me to describe my situation. I am on well water in a one bathroom house so the toilet really matters. The water pressure is quite low. The waste line does not have the desired drop into the septic tank. I realize this sounds rather rustic however the toilet (Kohler high line) functions well but it is time to upgrade. The Toto Drake sounds good but I'm also drawn to the cyclone flush of Soiree. This will be an investment so I would like to make good decision. Thank you for any imput.

Either one would be good for your application.
Drake flushes like a waterfall giving you a good flow.
Soiree flushes like a airplane toilet (without the noise) and also gives a better rim wash.