I'm by far not an advanced user, but I'll try to help:
If all you have is your PS2 that you're running in, you should still be good. On the back there's two separate plugin spots: One for your Component cables, and one for the Optical Audio out. Just run the component to your TV, and the optical audio out straight to your RCA home theater system. For normal TV, either your TV or your "normal" channel device (DirecTV/Dish/Cable) should have multiple audio out jacks. Just run a 2nd set of audio out to your RCA home theater system. Then, switch to RCA/A-V In for normal, and Optical for your DVD/PS2 time.
Hope this helps
EDIT: To expand on your questions a bit more:
RCA: Needs two cables, one for left channel, one for right channel. RCA outputs are a part of your PS2 COmponent cable. Coaxial Audio: Needs only the one cable. PS2 is not compatible with a coaxial audio cable. Optical Audio: Needs only the one cable. PS2 is compatible with a optical audio cable (sold separately, or included with your RCA system).
There seems to be this giant misconception about surround sound and analog (or SD digital) programming. I saw it alot at work when I was in home entertainment: most customers, and for that matter many employees, preached that you can only get surround if you have a digital coax or optical connection; no invitation for RCA cables.
All I have is a vintage 2000 Charter Digital Cable box by Motorola (highest connection: rwy RCAs) and a 1997 (really shitty) Zenith five speaker surround set. I get surround sound (though as Guru said, no sub track and my left and right rear speakers carry the same channel.) You need a better setup for 5.1, but if you've got as little as a rw audio out on your tube you can get ProLogic.