fairly new to the idea of wiring in sound, and electronics isnt my strongest suit, so i have some queries. i want to run a 4 channel amp for the interior speakers, and an amp for a sub install. any help to the below issues would be much appreciated.

1. can i connect 2 subs to a mono block amp, and if so does it use half the power for each sub, or will each one get the full rms of the mono block?
2. i know the usual fashion is to use rca inputs, but is using speaker level inputs on the amp still the same quality?
3. ive been told to run the power, earth and trigger wire together, and the speaker wire seperate to eliminate interference. how far apart should i keep them?
4. if running 2 amps, can i run 1 power, earth, and trigger wire into the cabin, and then split them off to each amp?
5. should i match the amp rms to the speaker rms, or have a lower rated amp than the speaker?
6. my car has premium sound, if im going to run twin 12 inch subs, should i pull out the factory parcel shelf sub and its amp?
7. my car is fairly new, (09 fg). im planning on getting 20% underdrives soon, will the battery cope with that plus 2 amps on top of all the other electrical goodies too? should i beef it up a little?

sorry for all the questions in one hit, i just want to make sure i do it right the first time.

#1 Yes you can and it will split the power between the two subs.
#2 Speaker levels inputs will provide the same quality in general, but i prefer RCA's myself since they are must more advanced designs out there these days.
#3 The way to prevent interference is to run all the cabling (including ground) on the opposite to power wire.
#4 Yes. I would suggest a 4gauge run into the boot/cabin and then split the power into 2 runs of 8gauge. (Actual size of wiring depends on power and amps you are drawing.) As for the earth just run 1 earth from each amp to the chassis.
#5 It all depends on the speaker, mine are rated at 75wrms and will happily take 100wrms since they are good quality speakers. Yes a general rule would be to match the RMS.
#6 Yes, never use 2 different type of subs in the same car.
#7 Since its a newer car it should be able to cope no problems. Maybe if you tell us what amps you are getting we can have a look at the power ratings.

cheers for the quick reply peaandham. not 100% sure on which amps, but i like the look of kenwood kac 8404, and the kenwood kac 9104d. reason i ask about speaker level inputs is i will be running these of the fg icc, which has no rca plugs. i guess i could use line level convertors, but being able to run the speaker wire straight in sounds alot easier. the 8404 would be running a set of rear alpine sps 600 (80 watts rms), and a set of kicker k6502 splits (75 watts rms) in the front. the 9104d would be powering two 12 inch pioneer subs. unsure of those specs, picking them up from a mate today hopefully. plan is to mount the amps under a false floor in the boot, (if they run cool enough, or under the front seats out of view.

No worries champ always willing to help.

Yes I agree that just using the Level Input will be fine if you dont want to mess around with RCA's and LOC's.

As for mounting they will run cool enough under the false floor or under a seat so take your pick.