The Win/MacOS/whatever software bundled with the drive needs the 300MHz, not the drive itself.
I had a Plextor PX-W4012TS in my A4k/CSPPC, worked fine.
Oh, and I also had an LG GSA-4163B on the internal IDE controller for a while. I seem to vaguely remember burning a couple of CDs with it, albeit slowly.
On the back of the box it says "Minimum Requirements: CPU P4@2.4GHz or Higher - RAM 512MB or Larger recommended - HD space 10GB or more - Direct X 9.0 or Higher - Videocard Memory 128MB or Higher recommended". Of these I had only the HD space, so I learnt two things from this revelatory box:
#1: My CSPPC@233MHz/50MHz could use the drive, ergo it must be able to meet the "Minimum Requirements", and therefore it must be at least as fast as a P4@2.4GHz :-o ;-)
#2: "Higher" and "Larger" should always be written with capital first letter. (I have no idea why. Thus were The Words written on The Box.) :-P