The shame is that Tube/Valve SECA designs are in the norm transformer coupled and this will lose top end and damping.
The old designs by JLH and Noel Keywood and in the Mullard design books are all choke and or capacitor coupled, this does limit there damping factors and BW.
With the latest beasts i.e. TOCA a large constant current load is used but the heat is high. The damping factor then can be increased to over 1000 as to 20-50 this sounds much better.

The output is 5 FET's in parallel performing a Source follow output stage and the driver stage is only a single transistor with a high BW and high current capability.

The control of the DC offset is another matter but no capacitor in the output or input path.  

10Hz - 100KHz is now easily met.

I to like Push-Pull FET designs but some can and do sound to harsh, one that come to mind was the Dr Thomas design and The Bryston.
All of them sounded like the raw unrefined Maplin/Hitachi apps note design.

Now the 300W MONO TOCA were in a class of there own, OK you did need you own substation but they did drive horrid loads, but at 1800W consumption each you would be broke after a good party. And big at the Penta Show people thought they were speakers at a 180KG each.

Here from the 2014 Thailand Audio Show are some large valve Single Ended Class A, note the size of the transformer, with the huge DC current to bias the valve into class and not saturate the magnetic core and drive it of zero you need lots of material.
But there is another way which I will discuss later and outperform convention.

I wouldn't want to mess with the anode caps on those

Martin,

It would just tickle once.
And with the music playing the dance could be called "SECA Night" so you would have started a new trend. Cool Dude.  

Ha !

Sorry to hear about the health issue

Not all Single ended amps suffer the same failings, you cannot pigeon hole one design over the other, its down to the designer, the design, and how it is implemented.

I've got a couple of SE valves, a couple of PP valves, a couple of PP solid state and a single ended solid state, and a couple of single ended SIT under development on the work bench. I know which one I prefer at any particular time but I'm pretty certain not one of them is any better than any of the others, to my ears.

Any one of them will sound pretty bad to me if connected to an unsympathetic pair of speakers.

My current passion is for stiff, choke input power supplies, and as far as the valves are concerned I'm neurotic about good dc filament supplies, preferably regulated. These areas even I can detect improvement when changes happen.

edit: Sadly(or not) I think I've got to the stage where I'm very complacent about amps. Anybody can play me a new amp but I don't think there's anyway they could convince me it's any better than what I've already got. It might be different, but better?...nowadays I'm much happier talking about the music. Maybe it's age creeping up.

yes and no, they have heat coefficients which determine their temperature rise against watts dissipated. The more suface area of heat sink, the better the heat dissipation. Usually the more fins, and hence the more air contact, the better the dissipation. A lump of metal is not the most efficient heatsink.

As an example I have a firstwatt F4 which is marginal on a figure of 0.26 degrees/watt. 0.26 is very very efficient and requires lots of large fins and 2 heatsinks 12" x 6" with 40mm fins barely gets rid of the heat....50 degrees above ambient.

That's a lot of heat dissipation area I knew Nelson's designs were somewhat what warm to touch lol

Interestingly the CE directives have a maximum outside temperature that the casework is allowed reach before it fails the test (and the CE approval), I could name at least five amplifiers that would not comply with this directive, not all are Chinese!

I have listened to Colin's recent little TQ class 'a' unit very nice with the right speakers it certainly does sing.