If we keep that in mind, then the setup of the problem changes significantly and most arguments made here do not apply to the download itself.
320kbit CBR MP3s were... I'd say, generally OK if you did not plan on skewing their tempo much outside of a very small range (give or take 5% speed). Really bad artifacting becomes audible quickly beyond that range. Maybe it was placebo, but I also found differences between FLAC and 320kbit MP3 discernible when working on big, more powerful speakers.
But, with FLAC, it didn't matter if the sound was played at 10% tempo or extreme amplitude, audio was always crisp, clear, and free of compression artifacts (obviously).
On my laptop speakers or earbuds, no way would I be able to tell the difference between any of these today.
This particular article doesn't touch on compression as well, which is probably the biggest thing for remixing or DJing. You really want uncompressed or at least high-bitrate AAC.
Could you expand on this?