Much confusion.
Some sound cards have dual purpose connector jacks that can be setup as either (for example) surround speakers or line out. If your particular sound card allows you to do this for the mic and line out then you're fixed.
/dev/dsp & /dev/dsp1 et al are sound channels under the OSS schema and are generally mapped back to /dev/dsp0 unless your card has hardware mixing and multiple onboard channels like a SoundBlaster. This method enables some magic IF you use full OSS ratehr than OSS emulation as found under ALSA.
So, if you have a SoundBlaster go to
www.opensound.com & get OSS (for free). Install it and fire up ossmixer; you now have as many indpendent channels as you want (I had 32) that can each be mixed separately and mapped separately.
If all you want is to hear two independent outputs through separate hardware devices (two sets of speakers) then you need two soundcards...one will be /dev/dsp and the other /dev/adsp IIRC
