My AX-7 is one of the very first units built. Last year, I had it upgraded to the "H" series production which includes the daughter board upgrade. So, I can't speak for the Evolution upgrade, but I can tell you that the H upgrade was quite audible, and I highly recommend it. As you point out, the AX-7 already sounds great. You could probably continue to enjoy it as is, blissfully ignorant of the upgrade potential. But now, you know that you could have even greater performance . . .
Regarding power cords, I upgraded the factory cord to Cardas Golden. It did make a small difference but I'm not sure it was worth the money (especially compared to the cheaper and more audible difference for the AX-7 upgrade). In my experience, upgrading the interconnect to my CDP made a much greater difference. I went from an RCA Radio Shack cable to the Ayre/Cardas XLS. WOW!
Happy listening.
Regarding power cords, I upgraded the factory cord to Cardas Golden. It did make a small difference but I'm not sure it was worth the money (especially compared to the cheaper and more audible difference for the AX-7 upgrade). In my experience, upgrading the interconnect to my CDP made a much greater difference. I went from an RCA Radio Shack cable to the Ayre/Cardas XLS. WOW!
Happy listening.