true 64 wma is not optimum for something you don't own, as i said i only do that for copies. However, winamp seems to play them just fine, but you are right in that a high quality mp3 would be a bit better..... personally i can't afford to buy 40 gig harddrives at the drop of a hat, so size is a problem depending on what you have on your puter.....for example.....at 64k i have taken up a few gig already and i've barely dented my cd collection, not to mention the higher quality mp3's of stuff i don't own i do have and plan to get. If they were highest quality most my harddrive would be full within a week.
So, just weigh up what each song is worth to you and what you plan to do with it.