Assuming, perhaps wrongly, you're more interested in playing tracks on a computer than in preserving quad quality, and assuming you have already go quad->DTS wavs.
VLC is a pretty good media player (Both video and sound) and plays DTS files out-of-the-box. Foobar2000 is best at converting files to other formats; it has a component called foo_input_dts (DTS decoder) which will read TDS-formatted tracks, and will provide the option 'convert 5.1 to stereo'. I use it when converting DTS wav to either Flac or mp3. The wav files are DTS, channels 3F2R/LFE, sample rate 44100, Bitrate 1411 k/s. The output is mp3, stereo, 44100, 320 k/s. Both the wav and the resultant mp3 play in VLC . Both are free: go Google them. I rate them both.
Now, playing pure quad. I assume you have original vinyl, or are you talking about a CD format?