I've had the WA6 running for 5 hours now, with the WU4GB in it. The copper cap is still cool to the touch, and every part (except maybe the bottom, didn't try it) of the WA6 is cool to the touch. Only things hot are the driver/power tubes. I'll try to put the same 5 hours on the WZ34 this weekend and see about it, but since I can't tell a difference, and Glenn says the WU4GB is better for the amp than the WZ34
Thanks.
I thought Glenn had mentioned that the WU4GB was better for the WA5 not the WA6, but I might have misunderstood.