I don’t know about the VASST tool you mentioned. If you have short movie and plenty of room on your DVD, then PCM uncompress 48khz audio will be best. If you want to save some space, set the audio as AC3. I’ve never had any bad audio issue with any of them.
You might want to check that your audio levels are not too high. Check the master level of your audio in your project(at least -10). Sometime the sound is ok on the computer, but when played on a tv set, the audio will distort if set too high.