B_limo, no problem, I'm always available to help a fellow 'goner if I can be of service! ;)
david is correct, the Ref 75 is at another level from the vsi75. I made my decision for my listening environment, needs and balanced that with my desire for simplicity, 1 less set of cables, no seperate pre, etc. I also was less sure of the audibility of the differences between the vsi75 and the ref75 in my home. My HVAC system isnt completely quiet nor is my refrigerator in the kitchen, nor is my neighborhood nor are the others in the house.
Anyway, you cant go wrong with the Prima Luna, the VSI75 or the Ref75 depending on what your desired price point may be. At the end of the day, the differences between all 3 amps is a matter of degrees. The laws of diminishing returns really do kick in in high end audio and you could certainly make a case that no one in the industry knows this better than Kevin Deal and Upscale Audio. The Prima Luna gear is terrific value and the Audio Research, while less of a value certainly delivers several degrees of extra audio performance but only you can determine if its worth the extra money. Good luck.