I had a chance to listen to the Audio Research I/50 at John Rutan's place last weekend. It was driving Vandersteen VLR CT's with a pair of REL T5/i's. Source was an Auralic Altair G1 I believe.
Very engaging system that really left me wanting for nothing. When I asked Jeff what the sonic differences were between the I/50 and the Rogue Cronus Magnum III he said the I/50 was more lush, romantic and tubey in comparison.
I may ask John for an in-house demo of the I/50, but I'll probably hold off until the winter. As my upstairs listening room can get hot!