The comparisons mentioned above were made between the Herron and Rhea, not the IO. The Rhea was a standard, not the signature version. The point I was trying to make is the tube compliment plays an important role in what your get out of the Rhea, more than the Herron in my experience.
As for IO tubes, I use all Tele's for the 12AX7's and the 6DJ8. The 6SN7's are Tung Sol. In the power supply, there are Russian 12AX7's and until recently Mullard EL34 XF2's. The Mullards have gone south so have been experimenting with different tubes in that position. One other thing to note about the IO. Mine started life as a signature. I replaced the coupling caps with Duelund Cast coppers and the loading resistors with Nude Vishays. I still need to deal with the output caps which are still stock.
As for IO tubes, I use all Tele's for the 12AX7's and the 6DJ8. The 6SN7's are Tung Sol. In the power supply, there are Russian 12AX7's and until recently Mullard EL34 XF2's. The Mullards have gone south so have been experimenting with different tubes in that position. One other thing to note about the IO. Mine started life as a signature. I replaced the coupling caps with Duelund Cast coppers and the loading resistors with Nude Vishays. I still need to deal with the output caps which are still stock.