[bojan]

This is very interesting..
However, it seems to me this system still needs specialised audio circuitry (kind of analogue decoder to separate channels for RA and DEC from audio card stereo outputs, and audio card must have 3 outputs, so it is not standard with only L-R) with amplifiers (one stereo amplifier per motor), capable of driving stepper motors (couple of Watts for higher torque).. so this is not off the shelf product.
Also, those audio adapters and amplifiers must be DC-coupled (for very slow moving steppers, while guiding for example).

I am using one of those programs mentioned in a text as problematic CPU usage-wise (Bartels, it has to run in DOS mode), and it works great, despite the fact that it requires dedicated PC (cheap 100MHz pentium, running DOS).. However, if I find some time I may try and have a look at this, just for fun..