Wire/Cables & Sub Choice

I'm prepping to install my system and I've got a lot of questions... I've done a lot of research and looked at all the stickies but seem to be lost in a lot of the explanation.

First of all... here's what I have:

Amps:
- Pioneer Mono Amp for Sub (600w @ 2ohms) [link]
- Xtant 2-Channel Amp for front speakers (50w @ 4ohms) [link]

Components and Sub:
- Infinity Reference 6010cs Speakers & Tweets (90w RMS) [link]
- 12" Infinity Kappa 124.7w (300 RMS) [link]
- OPTIONAL SUB (to replace 12" Kappa) 10" Rockford Fosgate (150W @ 8 Ohm) [link]

Questions:
1) I'm getting confused by the ohm ratings. My Kappa sub can switch between 2 or 8 ohms... but in the spec it says it's 4 ohm impedance. Is the amplifier's ohm determined by what ohm the connected speaker/sub is in?

2) I'm not looking for a tremendous amount of bass. Should I run the Kappa or the Fosgate sub. Please keep the power of the Pioneer Mono amp in consideration. Too much power for the Fosgate? Should I just go with the Kappa and turn down the power?

3) Wires! I went to Fry's but they didn't have anything larger than 16ga. I was recommended on another forum to use 4ga power wires, 8-10ga sub wires, 12-14ga speaker wires, and 16-18ga tweeter wires. Does this sound reasonable?

4) Fuses and Remote Lead. I was recommended to use 8-10 amp remote lead and an 80amp fuse. Any issues with going with a smaller fuse?

5) RCA's. Are Monster's really worth it? What are some good 'generic' brands that some of you have used that work well?

6) Where to buy wires, amp kits, sub enclosure? I checked out Fry's but they're limited on wire gauges (surprisingly). Any other recommendations? I was going to check Radio Shack tomorrow.

Thank you all in advance for your feedback!