Hey MBH,
Sorry for the late reply, I was away from the office for a week. For version 1.7 of Spark we decided to normalise the presets included in the standard version of Spark. All of the presets in VDM are all included in the basic version, as a result they were also normalised and this is the reason they sound different. All I can say is I'm sorry that this is having a negative effect on your projects and I hope it isn't too much of a pain in the neck.
Thanks,
Toby