From what I know ya two separate pair of are matched at within 5 to 7mA apart they are still able to operate... I would put a lower matched two at outer and hotter matched inner ?Since tubes are harder to find, and quartets are even harder, is there any issue with using two pair of KT77's? For the preamp is there any issue of using a regular 12ax7 instead of a 7025 in the VH-2?