Outputs when using Metra for GM Bose, sound horrible

[450.rider]

Its been a while since I ran my D3 in my truck due to switching back to my stock set-up when I planned on selling it but after installing it again I have a few questions. My subs sound like complete crap. I bought a brand new RCA harness before I re-installed the unit but they sound very muddy and crappy. Something else I did that was dumb was forgot to adjust the gain controls on the Axxess GMOS-04 adapter that is needed for my truck (03 Silverado SS). Basically with the volume on the unit at 35 it is semi loud but should be much louder. I am going to rip my dash apart Friday to do that adjustment but since the sub output RCA's are on the same harness yet run directly to the amp would this have the affect I am getting with the crappy output going on to the subs? When i was running stock HU with Bose and PAC GMOS-24 harness it would shake everything in the truck. The system consists of two Diamond Audio D3's and Cadence Z9000 amp pushing 800wrms @ 4ohms. Since it sounded fine before I put the D3 back in I am hoping the interface on the harness might have a roll in my issues but not sure because the SUB RCA's aren't connected to the interface at all.

 

I also wanted to know, where should I set the volume on the D3 through the interface. What is the norm for volume control. Should it be loud at 20 and tech max at 30-35ish etc.

 

Hope someone can shed some light because I don't feel like undoing the whole install because I have this thing strapped in to several spots so my HU can't get stolen again.