With very few exceptions (a couple manufacturers claim they will provide firmware upgrades in the case of a couple of their burners) current single-layer capable dvd burners will not be able to burn dual-layer discs or be convertable to do so.
As long as the original sound source is in 5.1 (or other) format then it can be burned as such.
If you are interested in dual-layer dvd then you should wait a while. There is still some ironing out of things that needs to be done.
Please remember to post back whether your problem is resolved or
not, so that others may gain from the knowledge.