Yeah most basic home users only need 80GB, but 120 would probably keep someone like you set for life. I think it'll come down to price cuz I think 80 would do you good, but if you do see a 120 for like 10 bucks more or something then I would say get it.
Yea i have an 80 and a 20 in my comp at the moment and those sizes u mentioned i would probably go for 120 might give u a bit of bragging rights , but im sure the 80 would be find aswell the way i look at it, its a win win situation.
Two 80GB drives in racks is the best thing to do. Forget bigger drives. Right now the technology is just not good enough... why do I say that? Bigger drives are more failure prone. They keep making them larger and larger, and they lose stability once they get very large like 400GB. People who get hard-drives that big are making huge mistakes.
Get two 80GB... for 160GB total if you really need it.