keep in mind that it has been a while for me picking out and installing a system.

Here is the beginnings of my new system...
Stock head unit in 2010 XLT
Infinity Kappa 680.9CS in front (tweeters mounted on sail in swivel mount)
Infinity Kappa 682.9CF in rear
The speakers are installed and bring to stock radio to life before adding power but for good measure I am going to install an Infinity Kappa four amp this up coming weekend. I still need to pick up the Metra harness, line out converter, speaker wire, and power cables.

now onto the questions
1.) If I plan on installing a mono amp and 10" sub in the future is 8 gauge enough to power 2 amps?
2.)The Kappa four doesn't have RCA outs, can I just split one set of RCA cables to the rear channel and mono amp? Should I buy a mono amp that has RCA outs and run to the mono amp and then onto the Kappa Four?

 

1. No, you'll want 4 gauge.

2. Of the two options, splitting the RCA is better then the two.

 

i would go with a diff head unit

 

I finished installing the Kappa amp with a line out converter and what a difference it makes. This system screams with 125 x4 RMS. I'll probably put in a mono amp and 10" in the spring when all the dust settles from the holidays.