The WA5 is bass light in quantity when driving the HE6 compared to an SS amp, specifically the EF6, and by a hair, compared to the WA5 driving the SR009. It's a known trade off for 300B single ended triodes. But the bass is absolutely there and on the right tracks the HE6s bass can be "oh my god" deep, impactful and amazing. It is obviously the better amp compared the the EF6 - better tonality, transients, resolution, imaging and soundstage. In any event I think it is not bass light in the sense of the HE6 not being properly driven - you can test this by comparing the HE6 being driven through the WA5's K1000 or speaker output vs. the single ended high impedance output (for normal cans like the HD800). Feeding the HE6 through the latter sounds ... horrible and completely anaemic in bass. As a disclaimer, I haven't driven the HE6 off 'real' speaker amps like the Krells or First Watts so I am not sure if WA5 is really close to the top yet in powering the HE6. What is more, you really need to spent a lot more on tubes (modern production premium 300Bs in the area of $500-$1000, NOS WE300Bs vintage around $6000, NOS 6SN7 about $300, and if you've sold your GECs and WE422, some premium rectifiers about $500-700). On the other hand, you don't get as much tube rolling pleasure with SS amps!