I only just discovered Mixx in the App Store and have it on my Macbook Air.. however my main machine is still a PPC Quad G5 running 10.5.8 !
I was so happy to see a PPC version, but found the same static playback issue with MP3's/etc. that others mention.
AIFF works fine of course.
I found a link to the last version of Mixx that works on PPC without the static.. version 1.9. Seems pretty good so far. http://moo.glines.org/mixxx/mixxx-1.9.0 ... macppc.dmg
Thanks for this great software, I wish I had an old PPC to donate for development.. I will ask around.