Avast is a virus in itself, IMO. I'd go without a virus/spyware suite before using Avast. All this being said, your best defense is simply using your machines in a smart fashion. People that open any email attachments in their inboxes will be infected regardless of protection software on windows, IMO.
I've used the ESET solutions for many, many years - both on my personal and business PC's and networks, and installed them on likely close to a couple hundred PC's for clients and I swear by it. It is not free, however - but most good things aren't. Kaspersky is great as well.
I've got a good number of associates that use the defacto MS offerings that come with the modern Windows revisions just love it as well. it works just fine unless you use your PC in buffoonery mode.
