Meh. AVG is sufficient. How many viruses are you really worried about getting, and where are you worried about getting them from? I go all kinds of places on the internet hunting stuff where there's potential for me to get stuff, and I've never had a problem just using AVG for a long time now. It isn't a memory hog in my experience, doesn't do anything weird to your computer, it's free, it does a pretty decent job with the common stuff, and... it's free.
But yes, discontinue use of Norton products ASAP. I swore by them for years and years, and I honestly don't know what happened, but at some point they just became total shit and all their products did was muck things up. They used to be great. I used their full program suites and they took care of all kinds of problems, cleaned things up, made your system run nice and smooth... but somebody over there dropped the ball, because my blind faith took the leap to an updated version of some programs and they nearly destroyed my PC. I don't know about the virus scanner, I just stopped using their stuff altogether. Thankfully Diskkeeper is a good replacement for Speeddisk and AVG is free. The one thing I haven't found that I wouldn't mind having is a good registry cleaner. The old ones Norton had were bloody awesome, cleaning up leftovers from uninstalled programs and that kind of thing, but that went south like everything else.