Old MPCNC Upgrades?

Hi all, I have a MPCNC I built a Loooong time ago and I want to upgrade the spindle, Im a bit worried about the extra weight.
Mine uses 25mm dia. stainless tubes, span is about 630mm across, the motors are 17HS19-2004S1.
The spindles Im looking at are 3.5kg and 6kg.
Would I have to upgrade anything else?
TIA!

Hey there, that axis seem pretty long for 6kg. Maybe just see whether a LowRider is in und budget?

Thats what I was thinking, the 1.25KW version is 3.5kg, might give that a go.