Need help in picking a surround system

[Grisle]

I'm looking for an entry level system that will best fit my needs. I have a very small entry level Home Theater which includes A 42" Vizio LCD, Ps3, X360, Tivo series 2, Comcast HD Box, and a wii.

I need a system that costs $300-$400...I know I have very limited options because even though I'd like a wired setup my wife doesn't want any wires. Does anyone know if the Onkyo SKS-HT540 7.1 Surround Sound Speaker System can be converted to wireless rear speakers?

I have very limited knowledge in this area so any help is greatly appreciated. My biggest preferences are the Ps3 and the Comcast Hd Box...I don't know anything about the optical outs and all that so I may need an explanation on whether a certain system will give me the surround experience. Also if there is a Home theater in a box without a dvd player I'd be interested in that because I use my Ps3 anyway. Please forgive my ignorance on this issue...I searched around and figured it'd be best to make my needs known as opposed to looking at someone else's.