I will say this, I have had at least 4 different lines of speakers over the years on our display board from Pioneer (sucked), Infiniti's, JBL's (best overall sound through all sizes), and now Quantums (suprisingly cheap, dependable, and loud). ALWAYS, the 6X9's reproduced louder mid-bass (and of course the lower bass tones) than the 6.5" or any others. And actually, the current Quantums Solar Series 6X9's are triax, and the 6.5" are only coax. A display board is an excellent way to do a true back to back test. Leave the same head unit, same volume, same tuning, and just hit the switches back and forth between the two different speaker sizes. Go by your local CC or Best Buy and try it-see if you agree. Again, this is just a generalization...