Excluding Bass Management, the sound is almost similar (the difference is due to the different DAC/Op-amp of the soundcard). Using ASIO, the full range/limited range option in drivers/Windows is just ignored (like all the other driver settings). The sound is always sent to each channels as it should ("full range"), then the sound goes into the amplifier that should manage the bass and re-directs the lower frequencies not covered by the satellites to the subwoofer (using ASIO as the output module you can be just sure that both drivers or Windows aren't messing something).
With digital connection and stereo analog (Aux-In/CD-In) this works just fine. The digital and stereo analog have the same amount of bass frequencies and sounds identical (apart the difference in DAC/Op-amp mentioned above). With 5.1 there's a strong lack of bass frequencies. This not only with 2.0 input, but with native 5.1 as well. In 5.1 the subwoofer plays the LFE channel but the lower frequencies coming from satellites are strongly attenuated (if not discarded at all). With 5.1 (Dolby/dts) coming from digital this doesn't happen and the sound plays right.

(Still, nobody contacted me. Let's see if in this week something happens)