You'll need high-quality cables to connect your amp, head unit and  speakers.  We recommend Monster Cable products:

		Monster Cable HPBAP-200 High Preformance 200 Watt Amplifier Connection Kit
		Monster Cable BAP-500 High Quality 500 Watt Power 4-Gauge Amplifier Connection Kit
		Monster Cable HPBAP-1000 High Performance 1000 Watt 4-Gauge Multi Amplifier Connection Kit
		Monster Cable BAIP-I201XLN-5M High Performance 201XLN Amplifier Connection Kit (2 Channel, 16.40 ft.)
		MONSTER CABLE Basic 4 Gauge Amp Power Kit; (APK-4)
		Monster Cable BAIP4C-I201XLN High Performance 201XLN Amplifier Connection Kit (4 Channel, 16.40 ft.)

Parts Express has cables and connectors for car audio and video systems.

Crutchfield cables:

• Audio Interconnects. For passing audio signals between components — RCA-type patch cords, and more.
• Subwoofer Cables. For connecting your powered subwoofer to your A/V receiver's subwoofer output.
• Audio Cable Adapters. RCA Y-adapters and other handy items.
• Optical Digital Cables. For connecting two components with optical digital audio jacks.
• Coaxial Digital Cables. For connecting two components with RCA-type digital audio jacks.

More cable suppliers:

• A2Zcables.com
• BetterCables.com
• Cables To Go
• Cable Wholesale
• Synergistic Research
• Electronix Warehouse