MK2.5S Upgrade to MK3S+  

RE: MK2.5S Upgrade to MK3S+

Upgrading your MK2.5S to the MK3 platform can improve performance and functionality. The MK3 includes upgrades that make the printer run more quietly, such as a new extruder and stepper motors. These upgrades can help reduce noise and prevent issues like filament jams.

RE: MK2.5S Upgrade to MK3S+

I'm in the process of doing this now.  At the moment, the MK2.5S is still in one piece, but sitting next to it is:
a black 24V PS
A 9 point Y Axis Bed
A 24V MK52 PCB
A MK3 Einsy Board
a 24V heater element
MK3S+ filament sensor
Spare SuperPINDA

Also sitting next to it is a partially assembled Bear Full upgrade.  All this started because I ordered the MK3s+ -> MK4 upgrade, and wanted to use the left over parts from the MK4 to improve the MK2.5s.  Now I'm sitting here wondering which printer to start disassembling to complete the Bear upgrade.  I have enough parts to make two complete MK3S+ printers.  Do I take the X Y and Z rods out of the MK2.5s or the MK3?  It only had one problem in the time I've had it, and I fixed that (Y rods were 0.4mm too far apart).  The MK3 is eventually going to be torn apart to become the MK4, but that's a few months away.

My end goal WAS to wind up with an MK4 and an MK3s+/Bear, but now I'm wondering if I should spend the comparatively small extra money for pulleys, belts, and whatever odds and ends to wind up with an MK3, MK3s+/Bear, and a FrankenPrusa 2.5/3?

In your case, Zeb, you are probably going to wind up at a minimum purchasing the 24V PS and Einsy board.  If you just want the quieter motors, maybe you should look into getting trinamic drivers:
https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-hardware-firmware-and-software-help/tmc2130-driver-infos-and-modifications/

RE: MK2.5S Upgrade to MK3S+

Welchomatic, did you ever manage to do the Mk2.5 to Mk3s conversion? 

I'm getting ready to upgrade my Mk3s+ to Mk4 and seems a lot of useful parts to replace on the 2.5s sitting next to it, post-upgrade. 

Wondering if you had success.  I would likely keep the 2.5s frame and just upgrade the electronics mostly.

Aaron