replace or up grade? I have not sold a tractor......only added :).  Are you looking to stay in a specific color?
Grew up with JI Case. So have pretty much been fond of the CIH's in my shed.
Biggest concern for me would be finding one that has not been run through the ringer. I will not buy used tractor
that has been married to a loader most of its life. Staying away from DEF and to much electronics are also on my radar.
Good Luck