Devilboy - We retubed the Titans with Russian (Reflector/Saratov) NOS EL84M tubes rather than anything else because non-M tubes cannot really handle the anode voltages that Kora has selected. In addition, the voltage issue is exacerbated by the fact that generation 3 Koras and earlier have 115V primaries, which ups the voltage from 400 to 440VDC (and 100mA bias). This is not a happy scenario for a regular EL84 tube and I'm sure the Jupiter is the same as a single Titan.
To be fair, many amps have 115V primaries but it's not a problem unless it is a vacuum tube power amplifier, and, you are running the output tubes at their absolute maximum operating point. I trimmed the plate voltages on the Titans back down to 400V (and heaters to 6.25VAC) but Ms are still necessary. Non-M EL84s will work for sure but their life will be shortened by half or so, maybe more. If you have any questions about all this, feel free to contact me directly.
But they are incredible amps - you made a stellar choice! Kora sound is truly special.
Arthur