I used to have the DEQ-7600 and DEH-P6000 and I think the manual states to set the volume on the eq to 23. Then you can turn the volume up as needed. I had the 3 band parametric eq adjusted as well as the 15 band eq. I REALLY REALLY enjoyed that eq. I would'nt use the eq to adjust the volume, don't set it to 30 either(makes a hissing noise is you do) Set the eq to 23 and control the system through the headunit. My setup sounded REALLY nice.....IMHO
Source: Premier DEX-P9/Pioneer CDX-1270
Processors: Premier DEQ P9
Front Stage: Orion HCCA 6s
Front Stage Amp: Orion Xtr 500.4
Subwoofer: Orion HCCA 15
Subwoofer Amp: 1 Orion HCCA 275g4
All in an 88 Toyota Supra Turbo!