Definitely beyond my capabilities, but here is what I found.
Thank you for providing the cost of changing the engine mounts. I may have to go down that route. As the vibration has some mechanical origin.
About the vibration: The car vibrates in the 1200-1400rpm range, particularly when I push the accelerator pedal to get more power, like a climb. I was testing yesterday with the DSG, and when in 4th, 5th, 6th at that range, when I push the accelerator pedal to 60-70%, it shakes noticeably, and it is very clear on a climb (I can't press it fullly because then the DSG will down-shift automatically even in manual mode). Otherwise, it is independent of speed, and as I just changed the wheels and tyres for summer, independent of those.
Looking at the forum, it seems the source of the vibration may be the engine mounts, or the air intake. Any other ideas are welcome though!