Given that is a Jensen amp the 300w number is probably peak output which is meaningless for the most part. The rating your interested in is RMS power output. The Jensen probably puts out less than 150w RMS. Post the exact model if you can. Power should come directly from the battery. The +12v wire from the battery should be fused within 18" of the battery too. For the Jensen 10 gauge wire is probably adequate but you might want to consider a larger wire in case you install a more powerful amp in the future or install an additional amp.thanks for the help man, i actually picked up a jensen 300w today. now all i need to do is wire it up, any simple guide on how to do this ? im a little confused about where im going to be getting power from.
RF has a wiring wizard here for the woofer: Rockford Fosgate® - Woofer WiringWizard Make sure you pay attention to the ohm ratings of the amp and woofer.
btw it will be tough to get descent sound out of a 12" and 15" playing together like that.