I'm hoping it'll address this problem that a bunch of us are having with Backup 2.02:
http://discussions.info.apple.com/webx?14@570.VzFFaG8BLvb.1137029@.689ccc78
and
http://forums.macosxhints.com/showthread.php?t=33884
You'd probably have better luck posting on the Adium forums. You may event want to look through the member list for Benjamin and shoot him an IM or email, he runs the Xtras site and knows all of that stuff, but i'm sure you'll get a quick answer with a post at the forums.
I would recommend Virex, however, i don't run any AV software since there still has yet to be one reported virus/worm for OS X. Running AV software on a Mac is done mainly to protect your PC using friends from virii that you may mistakenly pass on to a friend of yours who is not as fortunate to...
Norton programs are notoriously bad on Mac and most have been discontinued. Personally, I'd stay away from them, myself and many others have found that they are more trouble then they are worth on Mac.
America's Army takes up my whole PowerBook screen -- unlike many games. Even though the iMac isn't a gaming machine i doubt you'd have problems running it, as the game is a few years old now. Which video card do you have?