Yep, you bought right methinks. A lot of vendors suggest buying their speakers in that manner. Dipoles for the sides and regular speakers for the backs.

But you could have gone with 4 bookshelves and would have been good that way too.

I would stay away from dipoles all around for the 4 rears as you would lose a lot of the directionality that you get with the way your system is set up now, which is, I think, one of the points of a 7.1 system vs a 5.1 system. More front to rear and rear to front effects. Those kinds of effects, one would expect, would get muddied if you had dipoles in the rear.