Hi,
Not a question, just some info for those who are wondering about using these two sound cards together. I seem to having this working on my system, I'm using Cubase SE.
The history is that I had an Audigy 2 ZS Platinum Pro that unfortunately KX does not fully support. So I pulled the Audigy from my system and bought the new EMU Proteus X synth which comes with an 0404 sound card. The EMU worked fine in my system, but the Proteus X synth loads the system terribly (it does not run on the sound card as the SB synths do). Further, the MIDI timing is a bit sloppy. I wanted my Audigy synth back so I would have a zero CPU load soundfont player, so I said the heck with it and put the Audigy card back in (along with the 0404). KX recoginzed the card an re-enabled itself without messing up the EMU drivers and EMU mixer (Patchmix DSP).
I cleared the DSP window fed the Audigy MIDI synths (ASIO 2/3) to an FXmix2, and the MIDI effect sends (ASIO 13/14) through appropriate effects (reverb and chorus) to the same FXmix2, and fed the output of that to SPDIF. The SPDIF out is then fed to the EMU SPDIF in (via a coax cable).
All audio goes through the EMU 0404 (as it did before) but now I have the Audigy synths available as well. I'm using kxsfi VSTi wrapper (kxsfi.dll) in Cubase SE (although the KX version is 3537, but it seems to work!). Cubase SE uses the EMU ASIO driver for audio, so the EMU is still the sytem sound card, the Audigy is just an extra HW synth engine.
Just my experience, your mileage may vary.
Hope someone finds that useful, I know I would have.
BTW: One more hint is to use the "System Restore" feature before trying HW changes like these in a working system. Set a "restore point" first. Makes it a lot more comfortable to experiment (which seems to be necessary).