Thanks for the information guys, helpful as always.
I am planning to put these 2 in some hd15 style cabs I have built, with another 2 of the cabs loaded with Eminance kappa 450w. I have a Peavey 2600, 900w a channel at 4 ohms to power them. I know this isnt ideal, but its for something with friends and not hire outs, and my budget is poor! The obvious negative of this to me is the sound quality difference from the mis-matched speakers, but why, if at all, is loading cabs with different drivers a no no?