FWIW they wouldn't be rear speakers until you go to 7ch, they're just "surrounds" in 5 ch (and don't belong in the position rear surrounds do).
I'd think either of those would work as surrounds, as would many others (I often just have used whatever speakers I have left over from previous incarnations, true trickle down
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
). More critical to match your L/R with a center, so biting the bullet some more with LM centers may be the best route there.