mini_mull
1/2 ton status
It seems like most people put 6x9s in the rear of burbs and K5s, but I've never heard an explanation of why to pick them versus a 6.5" or other round speaker. Opinions please, thanks.

And you ahve the exact right thinking imo, spend most of your speaker fund cash on the fronts, leaving just enough for decent/good rears.
Do NOT spend alot on rear speakers. The front speakers should dominate the system, not compete with the rears. Remember, we listen to stereo recordings, 2-channel, not 4. Adding 2 rear channels actually hurts stereo imaging performance. Even when talking to someone who prefers the sound of strong rears, I never recommend spending alot of cash on them. Rear fidelity? Not too important, again the front stage should dominate the system.
Pop some decent coax's back there, whatever size you want, and call it good.
