The only challenge is to find other speakers that can come close to keeping up with the Jubs in the front 2 spots on L and R.
Have used Fortes, LaScallas and Khorns for rears. The larger the better they seemed to do.
Have used both Palladium 27 C in front, and a LaScalla up front also. Both worked pretty well.
Ultimate set up would be Jub x 5, if I had the room and cashola.
Or Jubs x 3 up front, and then the new 396's as surrounds and rears for a 7 channel set up.
with a 1502 or 1802 somehow in the mix also!