5.1 Home Theater for Audio for PC

Wil it work: yeah.
Will it do what you want is what you need to look into.
For example this is in the owners manual:

For Dolby® Digital Plus, Dolby TrueHD and DTS-HD multi-channel audio playback:
- An amplifier/receiver with a built-in (Dolby Digital, Dolby Digital Plus, Dolby TrueHD, DTS or DTS-HD) decoder.
- Main, center, surround speakers and subwoofer as necessary for chosen format.

Also I beleive it only has 1 input but you can read the manual.
http://www.lg.com/us/support/product/support-product-pr...

The way i would connect everything is using an hdmi input on the ht system to connect the pc and an hdmi output from the ht system to the TV. Then wire an optical digital audio return from the tv to the ht system. You can use any additional hdmi inputs to the ht system to connect consoles or other video/audio signals to the TV.

According to the LG site:

http://www.lg.com/us/tv-audio-video/home-theater-system...

there are no hdmi inputs on that particular ht system.
My advise to you is to get a home theater system with one or more hdmi input ports. Believe me , it will make your life much easier.

Note that the hdmi port listed in the specs is an output and not an input one, meaning you can use it to connect the ht system to your tv but not connect anything TO the ht system.

can i use the optical digital out on my motherboard into the reciever then just the hdmi out from my gpu to the tv and it should work?

I did this a few months ago (for 7.1) The biggest issue is having the proper inputs and outputs.

It works best if you have what they call multi-channel inputs on your receiver. This is a set of 6 (or 8 for 7.1) rca inputs. To use them, you'll need a bunch of mini-jack to rca adapters. The thing is, most new receivers don't have these inputs, they were more common back when component cables were standard for HDTV. You can still get them today if you look for them, but they usually only come on high-end receivers.

As a side note, it's fairly common for the sub not to have a signal when going the multi-channel route. This is easy to fix by looking for an option called "Bass Redirection" on your sound card's menu.

If you decide to go the optical route, you will need a sound card that can encode to either Dobly Digtial Live, or DTS connect (otherwise you just get stereo). The sound quality isn't as good as multi-channel, but it's not bad. Try either a sound blaster x-fi titanium (or better) or an asus xonar (read the fine print.)

I hear mixed reports about using HDMI from a video card. Theoretically, it's the easiest option, so try it first. But you might find the audio is lagged.