Thanks everyone for the recommendation on WA5. Also many thanks on the tube advice! I am not in U.S. and I can found a used WA5 locally but not the maxxed version. Not sure if I should try the buy/sell forum.
I have ordered a pair of Elrog 300B on the way. Picked up one Brimar 5Z4GY locally for my DAC (clarity and balance! what a steal!). Too bad my order of 5 units at langrex has not been delivered after 45 days. Hope they are not lost during the transition.
By the way, I am planning to use WA5 to drive lowther/voxativ full range drivers (98DB) and AKG K1000.