What gauge wire?
 

I just became the owner of a sony xplod XM-DS1300P5. It's an 800 watt subwoofer-specific amp. I already have an 8-gauge wire running from my battery to my trunk because of my previous amp, but I'm not sure 8-gauge will cut it with this new amp. I don't want to hurt the amp. Any suggestions?

8 gauge should be fine. That amp isn't that monstrous to require 4 gauge.

I'd go with the 4 gauge.. but either gauge will do fine

4 gauge would probably be safer, but if u really dont feel like putting the effort, 8g will probably to fine.

A quick search shows that amp is fused for a 60 amp peax (2 X 30 amp fuses) and that Sony recommends using an 80 amp fuse at the battery.

That kind of load would suggest 4 gauge, which is what Sony has designed the terminals to work with. That said, in my experience you could probably use 8 gauge with no issues since you'll seldom be pushing it at peak load.

A handy little site for working out wiring requirements can be found at: http://www.powerstream.com/Wire_Size.htm

Well if it truely has an 800w output, input would be slightly higher. 800W/12V=66.666A. According to the electrical code #8 is rated for 45A continuous load so while it will work it would not be ideal. #6 is rated for 65A and would work better. If you can not find #6 I'd go with the #4.

Very technical here, have to say automotive wiring doesn't fall in the NEC rule book and no one running audio is really going to run peak amps long enough to melt the wires. At peak the speaker will be destroyed long before the wires melt down. 8 gauge is workable, 4 gauge would be better but not really needed. 6 gauge, I haven't seen any places that carry or sell 6 gauge for car audio installations.