A little sad to see Webroot not even as an option in your selection above.
You are going to want something that utilizes low resources and provides the same protection even while gaming. Webroot can deliver that as it's a small, and utilizes just about 5 megs of memory while running, and about 12 megs during the scan. Not to mention that when there are updates to definitions, they are all done in the cloud and don't get downloaded to your computer.
Here are the results of the PassMark study in graphical form - http://www.webroot.com/En_US/resources-competitive.html