Generally speaking, smaller size means worse quality. Anything between 180 and 200 kb/s is decent, below 150 and it sounds bad, above 225 and for
most music, you end up taking up more space for diminishing results.
On the hd space side. My freind just topped 2 terabytes of hard drive space. About 1.75 are filled with things you don't want your mother to see...

Not me though. All 140GB of my used space are legal music and games.