What about having a non-Knoll fabric put on your sofa? This would open quasi infinite choice.
Have you already decided on the Knoll? If not:
Design: Flemming Busk, Stephan Herzog. I assume its pretty hard to get in the US but at a price point of roughly 1800,00 â‚¬ (with the basic, not-so-cool 10% acrylic fabric on; but they also have great tweeds, flannels, loden and leather) one could live with the shipping cost I guess.
I am actually sitting on this one right now. It's sturdy, very high quality and reduced to the very basic of construction. More sofa, less tech.