most VIRUSES came from files you download, not from a 3rd party trying to port in to your machine, so in that regard, no a router wont protect you from a virus...
ESET NOD32
and
AVAST
are the 2 ive used extensively and really prefer. very minimal load and they dont make a lot of fuss for no reason (like Nortard and MaCrappie)
AVAST is free, you DO have to register it every year, but it is in fact totally free, and so far I am very pleased with it.