I did some support (10 minutes worth) for the local volunteer fire department where their printer was failing due to ink build-up on the print head and arm area. This was probably due to cheap cartridges they bought on E-bay. They had a box with 30-40 of them in it.
They had bought them in bulk on ebay and they were getting old waiting to be used. I think they went bad in the box and caused issues in the printer.
Sometimes a bargain isn't really a bargain. Buy one or two and try it out, but keep an eye on the innards of your printer for things like leaking ink, etc. It may not be immediately obvious that there is something wrong until the printer stops working.
If you're going with AVG, I totally reccomend paying the $40 for a 2 year Pro license. I found it is better than the free version, especially with email scanning. Anyone who puts NAV on their PC deserves everything they get. :)