It may be more important to match the center and L/R than to match the center with the surrounds.
I'm running a B&K tx4430 for the front (L, C, R), and a Parasound HCA1000A for the rears. It's quite nice, and it's nicer than when I was running a 5 channel B&K AV5125; and also nicer than when I was running a Parasound HCA1203a for the fronts with the HCA1000a for the rear. I think the fact that the center speaker, and rears are different than my mains introduces more "nuance" than the fact that I have 2 brands of power.
I used a Levinson 27.5 to power a pair of Thiel CS2.2 front speakers and a Bryston 2B bridged for the Spendor center channel (older model; better than the current models, different design). A PS Audio 2C was used for the surrounds.
It worked very, very well once the outputs were matched with the processor channel adjustments. It worked better than a dedicated Parasound HCA1206 6 channel amp which I replaced all of the other amps with in an attempt to streamline the system. The Parasound is gone.