What is your sound setup? ARC is primarily for when you are connecting an AVR to the TV. You use an HDMI cable between the two and it allows audio from TV broadcasts to be sent to the AVR. It's called Audio Return Channel. It's only for TV broadcasts, but is def worth using. You need to make sure you set the AVR up so that it uses ARC though. It's in the HDMI part of the setup.
Also, it matters what kind of MB you have or whether you have a DD or DTS capable sound card. I don't have a MB that supports DTS like some of the new ones, and I don't have a sound card, so my AVR plays games in DPLII, since there is no DD or DTS encoded signal for it to decode.
If you're looking at 32" TVs, you may also want to consider the Vizio E32-C1. The LG you are looking at is only 720p, and has above average motion blur and input lag for a gaming display. It only gets a 6.2 rating overall, compared to 7.5 for the Vizio. On gaming specifically it scores 7.2 to the Vizio's 8.2.
The Vizio wins best budget priced 32" on Rtings.com, but is actually better for gaming than the Samsung that won best overall. Reason being with the Samsung you are stuck with either high blur, or high input lag, depending whether you have the anti motion blur feature on.
http://www.rtings.com/tv/reviews/by-brand/lg/ln530b
http://www.rtings.com/tv/reviews/by-size/32-inch/best