I think you have to really live with them, use them different days different amps if possible. No fast A/B I'm talking hours at a time. Now that would only mean you will get to know that one pair of 650s and really never get to have your experience of two different 650s that sounds different. Unless you have friends over and they bring there's.
I only know the 650s I have and the 1840s I have. I've lived with them for some time now. I fell I know them personally. I know what amps they like to sleep with and I know what amps they can't stand. I feel I can give an accurate account of these that I have.
Also, sorry I don't do graphs.