New compressor time

So we've outgrown our current 30HP VFD screw compressor and are looking at moving up to one in the 50HP range.

Models I'm comparing:
Kaeser SFC37T
IR R37ne
Rogers V series (50HP)
Gardner Denver VS40

So far from all of the quotes I've received back, the Ingersoll is least expensive package. On paper it looks very good, but I haven't been able to gauge how well they actually perform. Anyone have experience with a IR VFD compressor?