Welcome and upgrades are always fun!!
I guess I am a bit confused. You mention that you want to upgrade, but then ask for an equivalent speaker recommendation.
Let's try this. Since the M-490 is a bookshelf speaker, the Axiom (equivalent) sweet spot for your size room is the M22. The 38" height question doesn't come into play because they are around 19" and you will control the height of your speaker with the stand you use.
If you are looking to upgrade (go from a bookshelf to a floor stander)and get into the HT realm, then the M60 is a great choice. Sonically excellent. fits your room and also 37.5" tall.
