Filter Filters Sierra Remove All Filters Price $100-$500 (131) $500 and above (8) Condition New (139) Brand Harmony Audio (139) Make GMC (139) Compatible with 2007-2013 GMC Sierra Crew Cab Truck Harmony F124 Dual 12" Sub... $450.99 Compatible with 1999-2006 GMC Sierra Ext Cab Truck Harmony A122 Dual 12" Sub... $516.99 Compatible with 1999-2006 GMC Sierra Ext Cab Truck Harmony F124 Dual 12" Sub... $540.99 Compatible with 01-06 GMC Sierra Non-HD Crew Cab Truck Harmony A102 Dual 10"... $400.99 1988-1998 GMC Sierra Ext Cab Truck Harmony R104 Single 10" Sub Box & CXA400.1 $281.99 Compatible with 1988-1998 GMC Sierra Extended Cab Truck Harmony F104 Dual 10"... $399.99 Compatible with 2007-2013 GMC Sierra Extended Cab Truck Harmony A122 Single... $401.99 Compatible with 01-06 GMC Sierra Non-HD Crew Cab Truck Harmony R124 Dual 12"... $321.99 Compatible with 1999-2006 GMC Sierra Extended Cab Truck Harmony F124 Dual 12"... $460.99 2007-2013 GMC Sierra Extended Cab Truck Harmony R124 Single 12 Sub Box &... $285.99 Compatible with 1988-1998 GMC Sierra Extended Cab Truck Harmony R124 Dual 12"... $351.99 Compatible with 1988-1998 GMC Sierra Ext Cab Truck Harmony F124 Dual 12" Sub... $544.99 Compatible with 1988-1998 GMC Sierra Ext Cab Truck Harmony A102 Dual 10" Sub... $469.99 1988-1998 GMC Sierra Ext Cab Truck Harmony R124 Dual 12" Sub Box & CXA400.1 Amp $401.99 2001-2006 GMC Sierra HD Crew Truck Harmony A102 Dual 10" Sub Box & CXA800.1 Amp $479.99 Compatible with 1988-1998 GMC Sierra Extended Cab Truck Harmony A102 Dual 10"... $394.99 Compatible with 1999-2006 GMC Sierra Extended Cab Truck Harmony R124 Dual 12"... $342.99 1999-2006 GMC Sierra Ext Cab Truck Harmony A122 Dual 12" Sub Box Enclosure New $275.99 01-06 GMC Sierra 1500 Crew Truck Harmony R104 Ported 10" Sub Box Enclosure $115.99 Compatible with 01-06 GMC Sierra Non-HD Crew Cab Truck Harmony F104 Dual 10"... $405.99 Compatible with 2007-2013 GMC Sierra Extended Cab Truck Harmony R124 Dual 12"... $357.99 Compatible with 2007-2013 GMC Sierra Extended Cab Truck Harmony A122 Single... $315.99 Compatible with 1988-1998 GMC Sierra Ext Cab Truck Harmony F104 Dual 10" Sub... $474.99 Compatible with 2001-2006 GMC Sierra HD Crew Truck Harmony R104 Dual 10" Sub... $310.99 123456