5.1 sound

Hello, I'm looking to add a 5.1 setup to my current PC gaming setup. I already have a Sound Blaster Z as my sound card. I'd like a nice 5.1 setup, and I'm unsure if I should get something like the Logitech Z906 (http://www.logitech.com/en-us/product/speaker-system-z906) or a home theater...

my pc is connected by 1.4a hdmi to hdtv hdmi arc and then optical out from tv to surround system. the pc only sees stero and does not give 5.1 sound option. may be edid info sent back from tv wich is a lg42640b tv. the tv is seen on wireless device as well and will play musioc using...