We had recorded Alpha Innotec back then as "good" - unfortunately, I have no concrete experience - we were also dealing with brine-water heat pumps at that time.
For the selection of the heat pump, I would take a look at the BAFA funding list, which lists the performance factors of all subsidized heat pumps. You quickly get an overview of which ones are efficient and which are not.
The list shows the COP (Coefficient of Performance) at different air inlet temperatures. It tells you, in first approximation, how much electricity you use for how much thermal energy.