Finally got around to building this. 6SN7 => 7027A => GM70. Really sounds sweet. First build is running with 820 volts. The second mono block will be at 1050 volts then I will switch the other one up in voltage. Using Hammond 1428SEA (5K) transformers. The low frequency drivers in my speakers are JBL 16 ohm E140's. Getting excellent definition on low frequency notes.