I just measured the TiR on my Kress 1050, and it is around 0,04mm.
This seems a bit high, is there anything you could do to improve it? I would guess this TIR is one of the reasons I have problems getting clean cuts in brass. (CZ120)

I am considering upgrading to a better spindle, does anyone have suggestions for moving up a notch?

The eBay watercooled "Chinese spindles" seems to be quite a gamble, I would prefer a spindle with a warranty that counts for something.

Regards,
Hauk