I'm sorry I cannot help with the question itself, but I wouldn't be convinced that it's the server configuration.
I have a small QlikView application on my server (4x10 CPU at 2.8GHz, 512GB RAM).
Against my advice (and our best practices), this application contains multiple embedded IF expressions with aggregations, as well as calculated dimensions and formatting of similar complexity.
Not only is the solution slow, it only take 5 concurrent users before I see an impact on the QlikView Server performance as a whole. I can actually watch CPU usage spike when users make filter selections.
I am trying to isolate the problematic expressions now.