Not sure why you want to use a mixer in the path when you still have only two mics, (or a mic and an electronic piano?) which the EMU can handle? The mixer won't make it "stereo", unless you have a stereo effect plugged in to the piano or vocal mic auxilliary effects loop. If you are worried about it being panned vocal left, piano right after recording, you can always pan the tracks to the center. And, what that does is take an actual (technically) stereo (as in separate tracks panned) thing and collapse it to mono, anyway. Leaving them separate allows you to work on each separately with effects, levels, compression, etc. Once you combine them into one track (mono or stereo) you lose a lot of that ability.

Anyway, you need to assign track one input to the EMU left channel, mono. Track two should be EMU right channel, mono. If you are using the mixer and either channel is panned center, it'll go to both EMU inputs, and show up in both recording channels.

The more interesting thing you might try is to use the two mics to record the piano in stereo (or two mono tracks, left and right), and THEN record a third mono track with the vocals, centered. (This is assuming you are talking about having an acoustic piano mic'ed up. If you have an electronic piano, if it's stereo, record it first as a stereo track, then record the vocals?)

The way you present the whole thing is that you will have one of three things. A completely separated far-left and far right panned piano/vocal recording (which can can 'technically' be called stereo...like an old Beatles recording), a collapsed panned left and right piano/vocal recording that brings both closer the center...or a completely mono recording, centered coming equally from both speakers. You can't make "stereo" from a mono source, unless it's just effects trickery. With a simple piano and vocal recording, the piano should be stereo, and the vocals centered.

If it's monitoring complete left and right piano/vocals that drives you nuts, maybe try plugging into the mixer first, set your monitor levels and panning so you like it better, and then send the two channels' direct outs to the EMU. Those should still be left and right, pre-panning in the mixer. Set the inputs to Adobe from EMU track 1 left mono, track 2 right mono. After it's recorded, you can pan them anywhere you want.

Please elaborate more about what you have (mics, piano type, etc) and what you are trying to achieve. As is often the case, there is too little info to provide an accurate solution, so a lot of this is just guessing on my part.

Good luck,

Kapt.Krunch