rear speakers to compliment 6.5 qsc's

I'm running a set of MB Quart QSC's in front and have a pair of 6X9 Kappa's in the back that I'm looking to replace. I'm debating on whether or not to just get another set of these for the rear, but don't want to drop 250.00 for rear fill. They will be getting 125W RMS just like the fronts, but I like the fade to the front a bit because of the imaging. Is there a set of Quart 6x9's I could use that wouldn't be much different in sound, or should I just get another set of comp's now that they're on sale at ikesound for 250.00ish shipped?

I personally woudln't spend $250 on rear fill. It's just that, rear fill. I like rear fill as I have passegners and enjoy the increased volume, so my solution was a lower line from Rainbow to compliment my fronts. I would however try to at least stay with the same tweeter material in both sets.