This is new to me that DVDs also include a stereo soundtrack. My DVD only have the 5.1 one. 5.1 english and 5.1 german. And the german movie I have has 5.1 german dolby and 5.1 german dts.
If the DVD contains 5.1 sound then I highly doubt it'll contain a stereo sound. There is no problem playing it back on stereo speakers (I don't have a 5.1 surround system either), so don't worry about it
RJ