Many low end soundcards have hardware restrictions on the input/output flow. Circumvent this with hardware schematics and a soldering iron.
However, it's possible your soundcard supports input and output on any (or some) of its ports, and you just need the software to do it. ALSA and OSS provide the kernel drivers so other software can access the card. PulseAudio and JACK are two different programs that let you play with streams of sound. It's likely that if you invest a bunch of time reading manuals and editing configuration files that you can do what you want.
You may also want to check out Ubuntu Studio. It tracks with the mainline Ubuntu releases, but is set up with a bunch of packages that professional audio folk bent on using open-source linux software would use.
Ubuntu uses PulseAudio because of its focus on desktop audio. Ubuntu Studio uses JACK because of its focus on sound production.