if vocal or song is the main listening, I would keep 950. It has more bass presence, offering a more lively feel . However, classical music, (particularly, symphony, choir) is the main listening, then Stax is the better choice. the soundstage is more 3D and defined, you can tell the position of various instruments more easily. Bass is less "touchy" than 950, but it is there. Say, if there are multi-number of drums on the stage. The sound from bass drum and than from snare would be more easily picked up and positioned by Stax than 950.
to my ears, Stax is less lively but more natural, sound is also more "accurate". Its very much like "kodak film vs fujifilm" in the old days. Kodak gave you more red and hence, much richer tone. Fuji less red and more green, less eye catching, but more natural. Hope you can "feel" what I am trying to say here.
I might risk offending some ppl here by the following statement, for the reason of looking for more natural sound, I marginally prefer older stax (srx mk3/ lambda pro/404 ) than modern ones (507/L300/L700). :)
Electrostatic headphones, stax/koss/kingsound have different character than traditional dynamic cans, keeping just one pair of cans (whether it is a dynamic or electrostatic) is not fair. You are being too mean to yourself.
Go and work harder, earn more and visit massdrop more frequently. My 2 cents.