It's all up to the individual, I personally consider myself somewhere between the average listener and a "golden ear" audiophile, so alt-preset-standard is fine for me, and I can only personally hear artifacts in a 128kbps CBR file on a really good system. The rule of thumb is if you can do a blind listening test and not hear the difference, then pick the smaller file. You're not going to impress anyone by having a higher bitrate, but you'll be very happy to fit more music on your empeg. Or that's the way I look at it, anyway. When I did my own blind listening tests, I found I could tell a 128k versus an alt-preset-standard a little better than 70% of the time, so I went with that. But a lot of times, in my car especially, I really wouldn't be able to tell.