If you're using it for a mill you need a 660 or 880. Other that that a MS261 would be excellent for the work you describe. If you want something bigger that can handle a bar longer than 20", a MS462 would be an excellent choice.
Does it really need to be that big?
If so, I’m not ready for that yet.
If yer just milling small schidt, no, but you will kick yourself for not getting a bigger and more powerful saw if you move up at all in size. Remember that you're milling with the grain rather than cutting across the grain - more power is always better in such cases. My logger Bud in OR cuts & mills BIG Western Red, Doug Fir, Maple, etc. and has some impressive rigs:
Custom 96" double-ended bar with dual 880s:
His small rig:
Also, if you are going to mill, do yourself a favor and learn the Humboldt bottom/undercut.