Is there a "best" practice regarding the sample rates? I understand music is typically 44.1khz, if I set the Xonar control panel to anything higher music will get re-sampled. Is this particularly a bad thing? Also, if I do change the sample rate to 192khz, am I supposed to also set this sample rate in the "Advanced" tab of the speaker properties?
I have also read that you should set the gain on the headphones to match the impedance, but was curious as to whether the potential damage is brought about if/when the output volume is set too high, or if simply setting the gain alone is enough to do it. I swear the cans sound better with the higher "medium" gain setting in Xonar, but am worried since it suggests "Normal Gain" for my cans (42 ohms).
Normally it is best to not resample anything because a./ there is varying quality between different resamplers b./ it is CPU-heavy on a PC. If you don't resample you just know the sound is ok,which is good for the mind!
If you choose to resample you must know what you do, and use a good resampler, normally one associated with the player you use and in the form of a plugin. Also, the setting in Windows control panel is only active if you run the Windows sound stack/mixer, which you shouldn't for music, use WASAPI or ASIO - selectable in the player - as they talk directly to the soundcard and should be used if resampling is going on. The new Soundblaster Z/ZxR even require upsampling if you run in the "stereo direct"-mode, which is only active @192kHz. In the Creative case "stereo direct" bypasses the DSP on the card and lets the drivers talk directly to the DAC.
So what are good upsamplers/resamplers? If there are any. It's debatable, but according to my own findings so is the standard resampling plugin in foobar2000 not the best out there(there is other plugins that can be used), I think it colors the sound ie no upsampling is normally better. There's better results using the built in upsamplers in uLilith and Musicbee imho. But the best upsampling for PC that I've found so far is the plugin in Deadbeef-player under Linux which uses the original "Secret Rabbit Code" for upsampling - I think it sounds excellent! Also, under Linux it's essential to use ALSA instead of Pulseaudio for playback. Like it's important to use WASAPI or ASIO under Windows, as those modes bypasses all sound stuff going on under the hood in the Windows OS.
For gaming sound you can forget all of the above, just use the normal recommended settings.
About the gain on the Xonar-cards, it is just gain and not anything else so it doesn't change any impedance or anything, you can just forget about what impedance is written in the drop menu and use the setting which sounds the best with your headphones. It's not strange if a higher gain actually sounds better, as the HP-amplifier on the Xonars is a small amplifier and all amplifiers sounds better with higher gain as long as it is under the clipping limit. Higher gain normally means lower distorsion and better S/N in the amp, it can amplifiy underlying noise in the source signal but the amp itself works better with higher gain. As I said, use what sounds subjectively the best!