Sorry Goran, I could not wait for your answer and just bought the aircraft ;-)
I can confirm your statement. My spec is clearly above a 2013 iMac and I had to set down the graphic settings, just to get around 22-24 fps (most plugins disabled, on Aerosoft LSZH scenery).
Here is my spec: Model: iMac (Retina 5K, 27-inch, 2017), CUP: 4.2 GHz Intel Core i7, Memory: 16 GB 2400 MHz DDR4, GPU: Radeon Pro 580 8192 MB
Here my graphics settings:
Just consider this a quick and dirty benchmark. From this quick check and based on my experience with other aircraft I can say that TBM 900 should work fine for me even though it is on the low end of fps and depending on scenery and weather settings/plugins I may have to fiddle with the graphics settings from time to time.
this is how beautiful the aircraft looks like, even with these mediocre settings ;-)