Radio replaced, but poor volume from rear speakers?

[MiatAndiamo]

I had the audio system (in-dash portion) replaced in my still-new '09 LGT, and now back to original quality. Now, notice very poor volume from rear speakers. BTW, I think it has always been this way, but am more aware of it as started to fiddle more with the system since its replacement. They did nothing with the speakers. I did look at the similar thread started by Crawdaddy 79 back in 2007. Am just wondering if that also applies to the 2009 LGT, which has the H-K system? I am not a true audiophile or knowledgeable in the intricacies of such things, but the only way I hear any "balance" is if I put the Fade at R4 or R5, which means I have to crank up the volume to get anywhere near the same sound/volume from the front speakers. It seemed that my leased '07 Saab Aero was better balanced, and that was a GM set-up methinks