You generally only want an audio system grounded in one spot. Having multiple grounds leads to ground loops and the resulting hum. Power amps are almost always grounded with a 3 prong plug, preamps are not.
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Main system:
Integra dhc 9.9
Threshold SA/4e pure class A
Emotiva XPA-1 (2), XPA-5
(2) Threshold S200's
Thiel 3.6 main speakers
(2)Velodyne F1500r subs
Polk RTI28 surrounds
B&W HTM center
OPPO BDP-83 universal player
Samsung HLT6187 led DLP