You should just come down and see my setup and either copy or improve it.

I too was once a noob at this stuff but after seeing a ton of other installs you'll slowly get an idea what works.

I'll try to snap a few picks of my install tonight to give you some ideas.

On another note, type-r powered to 100watts RMS fill really well. If your not into subwoofers, then you can probably live without it.

 

I agree with Dave-ROR, if you already have 2 amps then you can run those (1 for mids and highs and the other for the sub). You really dont need alot of power to run the interiors and some aftermarket HU's are decent enough for this. If you are running a 2 channel amp for 4 interior speakers that do not need alot of power you may also conisder running them at 8ohms which means you would have to connect them in series and not paralell (+ to + and - to -) Since space is a premium in our cars, maybe that would not be such a great idea. I am currently running 1 5channel Alpine to power 4 interior speakers and 1 sub in the trunk and it is quite sufficient.
Back to your question on how to run the 2 amps. Run 1 4gaguge wire from the battery to the trunk and then use a power block to split to different amps. this is a small black that may have individual fuses to distribute your power to different amps. You would also do the same thing on the ground side with 1 major connection to the body running to a ground block (no fuses neccessary) that connects to your different amps. There are some fancy looking power blocks out there that can dress up your installation. Again as mentioned before please make sure you use the same size wires for both negative and positive sides. This stuff is easy just double check everything before you drop in the main fuse under the hood.

Good luck and hope i have not confused you even more

 

There are a couple of big question to ask yourself in regards to 2 amps or 1: How much room are you willing to give up to install the amp(s)? Are you willing to give up your spare tire? These are very subjective questions, and you will find people on this site with exactly opposite opinions. My recommendation is look at the various installations that can be found on this website and get a feel of what YOU want.

Two amps will definitely give you "cleaner" sound, if you follow what has already been said (one amp for the mids/highs of the door speakers, and one for the sub). However, a single amp will take up less space. [Opinion on] I'm not sure with our cars, if the slightly cleaner sound of two amps will be noticeable as compared with a good single amp. [Opinion off]