Nice review Peter

. Made up your mind yet gb?
Some thoughts:
If I was buying new and given that both mounts are currently the same price (sky commander works with T-rex encoders) I'd get the T-Rex. If I could have a used DM-6 at 70% of new price I'd get the DM-6.
For most users the T-Rex is the better mount due to it's slow motion controls, though there are niche applications where the Discmount is better: the DM-6 can be balanced thus it can handle a C14; a pipe mount can be added to the DM-6 allowing two scopes to be mounted at once (photos coming soon

) and the scope can be mounted on either side of the DM-6 allowing a cassegrain focuser to be at the bottom of the ota.
All things considered I'd say just grab a T-Rex while the exchange rate is good and if you don't like it you'll be able to sell it easily.