Is the issue with DTS or both DTS and WAV? If WAV files don't play there is a big problem and the kmixer is not the culprit.
The kmixer matches sample rates and mixes multiple audio streams. If for example, you are playing a 16/44.1 WAV and at the same time click on something that would generate a windows sound (which is often 8 bit at a much lower sampling rate) the kmixer will resample the 8 bit audio on the fly and you will hear both sounds.
The realtec is a built-in sound chip on the motherboard, right? It is AC '97 compliant and thus works at 48 kHz. The kmixer will ensure that all streams going to it are 16/48. This is only a 'problem' if you want to record at say 16/44.1 because the chip will actually record at 16/48 and resample to 16/44.1 on the fly. For playing WAV files the process will be transparent to you.
DD/Dolby Digital is another issue entirely. Because the sound chip doesn't know that it is a compressed format, it thinks it is just PCM like a WAV file and the process of converting it to 48 kHz will destroy the encoding. ASIO drivers, which bypass the kmixer, are not the solution. You need a card that can identify a DD/DTS bitstream and just pass it through - and many new cards do just that. The SoundBlaster Audigy 2 and newer can do it and it sounds like the card mentioned can do it too.
Calling DD/DTS pass-thru 'bit perfect' audio is a bit of a misnomer. Bit perfect audio usually refers to recording; ie what comes in is what is processed without being modified in any way. ASIO drivers are used to get around the conversion to a different sampling rate for recording but for playback are not necessary.