Most of these questions don't have straight forward answers. I mean what objects are in those dlls and what do those dlls do? If there is just a user class and collection that seems like a bit many dlls for that. Also do you mean that these are all on a 'server' type computer and not where the 'client' exe is? Another question would be if so then what is the reasoning? Deployment?

Deployment is much easier in .NET since you don't have to register any dlls. Also you could probably get away with using the same dlls BUT to take full advantage of .NET you would probably want to rewrite them.

How are you passing the data to the UI now?

If you want to upload the VB6 version maybe one of us will translate it to .NET (providing it isn't too big a beast).