There's more than a hint of audiophoolery about that Decware beast. As a single ended low power class A triode (connected pentode) output amp it's no doubt fair enough but I would expect a Mullard 3-3 would work as well or better without all the gold plated waffle.
All of the stuff about speaker placement and room dynamics is of course equally applicable to any amplifier/speaker combination not just the wondrous Zen.
There's no mention of output power or distortion but Philips reckon on about 2W at 9% for a triode connected EL84! This of course compares very favourably with 3W at 1% for the 3-3
