I use a Vario and Pharos every day both feeding into a La Spaz. The Vario for wife's latte and Pharos for my espresso. With such a milk drink she couldn't tell the difference anyway.
With $1500 couple years ago for stripped K10 since I strictly single dose called Chris Coffee expecting to talk to Mary and Chris answered phone. After hearing me out he said, "don't purchase the K10 expecting to tell a difference in the cup compared to your Pharos".
That floored me. Have admired Chris ever since and always sing his praises.

With a 53mm portafilter the La Spaziale simply don't channel as a rule. What they say about the K10 needing serious break in has to be true since yours does channel.
And bolthead mark in center of your puck is common with this machine. I have settled into a routine of 16.5 grams from Vario and Pharos and a small indentation is evident. Nothing wrong with 17 grams and a strong indentation if you desire according to comments from La Spaziale owners site.
Out of habit I do WDT for a few seconds and have never had channeling after thousands of shots.
good luck!