I would rather replace the internal HD then the floppy drive, especially if you have the rare chance to upgrade to EOS 4.62 you needed it. E4K has a very good keyboard, one of the best I know, you had to spend some serious money to come across one which matches. I think with that EOS you mention
you're limited to HDs up to 18 GB I believe.
I you hated the FX of Emulator X I guess you'll hate the basic ones of E4K even more. The factory sounds of E4K IMHO are the worst Emu ever produced, so don't rate the unit by them, try other CD-Roms or sample yourself, to hear how good it actually sounds.
Where does that actually come from that bad MIDI-timing thingy ?
Because you read 'improved MIDI-timing' in a later EOS update-description ? So to answer your question from my side, NO the timing is not bad.
I bought my E4K brandnew when it came out, sadly in a way it acts as kinda dummy-masterkeyboard for playing in stuff only these days. I spend so much money for it, just won't sell it for the ridiculous money I'll get.