New Surround Sound System

I currently have a Hitachi rear projection Tv...about a year old

I want to hook up a Surround Sound system to it, so I can get my TV sound through it

I also have a cable box from my cable company and a ps3 to hook up

When looking for a System, what are the key features that I NEED to have?

Do I have to buy a system that has 2 HDMI inputs and 1 HDMI outputs? or can I get one with just a HDMI output?

I really confused on what to get, i dont want to spend a arm and a leg for one....i just want one that will sound good and work with what i have?

Thanks for any help!

My room is going to be 20x13........I want a complete system...i have about $400 to spend....give or take a bit

Since I will have a ps3 hooked to it...along with my cable box/maybe a blue-ray player....do i need 2 HDMI inputs?? Or is there a way around it...

I want surround sound for sure when watching TV and playing PS3.....if the system has a built in DVD player...then that will work...

So i guess im mostly wanting to know a good system for my price...and the one with the right specs...because alot of them that I have been looking at only have a HDMI output....or 1 input and 1 output?

Thanks