Hi Sugarshed. I happily owned a pair of Duntech Princess speakers for 19 years. They remain one of the most musically satisfying speakers I know of.
I had to replace two woofers (yes, Dynaudio) in mine following a DC pulse from a misbehaving amp. That was several years ago and at that time Dynaudio would only sell replacements to manufacturers, not individuals. I tried Madisound since they once sold Dynaudio drivers but they could not help. Eventually I got assistance through a manufacturer friend and found original replacements. Perhaps stories like mine are why you found a Vifa in your Marquis? I understood all woofers in the Duntech Classic line (not for Dunlavy Audio) were Dynaudio but I can't be certain.
As for removing your woofer, they are installed with an adhesive as well as screws to ensure they remain air-tight. After removing all the screws, use a wide blade screwdriver or stiff putty knife blade and gently work your way around the basket rim (use a stiff, thin object underneath to avoid pry marks). Pry just a little at a time and move along a few inches. That should work the speaker loose.
I'm very disappointed to hear of your response from Duntech. I believe they have new owners and that is no way to carry on the original reputation for customer support.