2nd time blowing these 6x9's

Judging from the description you just posted, you are blowing the speakers because you do not have the gain set properly and you are overdriving the amp, probably clipping like crazy, and burning the voice coils because you are sending DC to the speakers.  You should NEVER use amplifier gain as a volume control!  It is designed to be set ONCE to match the input voltage characteristics and then left alone.  It sounds to me like you simply are mis-using the system.  If you do not understand how to set amplifier gain, please click "SEARCH" at the top of this page and do a search for "Setting Gain."  There have been at least 50 threads on this forum that describe how to do it correctly.

Otherwise, you'll keep blowing those Quarts.

Since you're doing that, maybe the head unit is sending a clipped signal, Which at high volumes you WILL NOT be able to hear, this clipped signal gets amplified, heating your voice coils excesively...

You should set the gain down completely,  then turn up the volume on your head unit until you can hear distortion...  Then turn it dow a bit...  THAT is your max volume  (It doesn't matter if it's only 50% of what the unit says it's capable of). If you go beyond that volume, then the HEAD UNIT is the one that clips the signal, regardless of amp/gain configuration

After you have that volume set, turn the gain up until you hear distortion again... That is your amp distorting, turn dow the gain a bit until it dissapears.  That's it... never touch your gain ever again... And don't go beyond that set volume!