Per Elias's suggestion, I downloaded VLC. Bottom line, if you want to play your albums off a hard drive (which is all I ever do), it works.
On one of my systems I use a Mac PowerBook Pismo (500MHz, 512MB). It won't run Leopard, so Gordon Rankin's upgrade suggestion doesn't help (I will try the Leopard upgrade on my MacBook after Leopard settles down some more).
VLC is noticeably more clear to my ears than iTunes 7.5.
Two quirks of VLC really stumped me, so I will repeat the resolutions here for those who might want to try it on their Mac's.
First, in the Benchmark Wiki Elias says to keep the VLC volume control at 100%. OK, that is the consistent advice we hear (e.g, from Gordon, too). The quirk is that in VLC, under "VLC -- Preferences -- Audio" you will see that the volume can be set anywhere from zero to 1024. This volume control should be set at 256 because 256 = 100% or "0 db". If you set it higher you will probably add distortion because you are amplifying the signal. I made the mistake of setting it at 1024 (thinking that was 100%) and spent several hours figuring out why at that level the music was clearly distorted on my system.
The slide volume controller on the little VLC menu that pops up when you start VLC is a different matter entirely. It varies the volume level you have set in VLC Preferences. So after you set the Preferences -- Audio level to 256, you want to set the slider on the little menu all the way to the right, which gives you the full 256.
With these settings in place you will then use your preamp or other volume control to actually control the volume of the music.
Second, I suspect the computer guys would have gotten this in about 10 seconds, but if you select "mute" from the Audio pull down menu (or otherwise find that you have muted the sound somehow -- which I did several times) in order to unmute you just right click on the "mute" selection. Left click puts mute on; right click unmutes.
The big downside to VLC is that the documentation is very, very sparse. But I got it up and running -- and it is a solution to play Apple lossless files clearly, with low or no distortion, on a Mac that can't be upgraded to Leopard. If all you want to do is play your albums (and probably a lot more if you can figure out how to use the more advanced functions), it will do the job.
Thanks for the tip, Elias! Regards, James