Who tried Class D only to return to S/S or Tube

Kijanki, in your zeal for Class D I'm afraid you mischaracterize linear power supplies. Not all are cap input.

Choke input linear supplies do NOT draw power in "huge narrow spikes". In fact they draw power continuously throughout the conduction cycle, resulting in smooth, fast and clean power delivery. No "huge amount of capacitors" are needed since choke input supplies have very good inherent regulation.
I use choke input in everything I build, including amps, preamps, DACs, even for DC IDHT tube heaters. Best feature though is no RF nasties flying around the room, which are inevitable with high frequency switchers.

Ait, Choke at the input as well as choke and big capacitor in my Furman Power Factor correcting conditioner serve as filter. Charging Linear PS capacitors is still done in narrow spikes of high amplitude - no escape from that.  Current is switched on  and off when voltage is the highest (worst possible moment). Choke filters out spikes from the power cord but problems inside still exist.  Switching noise propagates thru the circuit affecting sound.  The only linear part in "linear supply" is that it is unregulated.  Output voltage still depends on the load while line regulation is zero.  I wrote about "linear" supplies, to show that switching can be done smarter in SMPS that has very tight line and load regulation - usually not possible in power amps linear supplies because of power dissipation in voltage regulators.  There are great sounding amplifiers with linear supplies, even without any input choke.  I’m only stating that it can be done better with quiet SMPS.  Switching supplies designed by Jeff Rowland are extremely quiet.  FAQ on his website explains why he abandoned traditional "linear" supplies.

http://jeffrowlandgroup.com/kb/questions.php?questionid=145

Kijanki,
I believe you misunderstand what a critical inductance choke input supply is. The input choke serves to smooth the current draw - I have attached two simulations of the power supply I use in my amps showing the current draw in the first power supply capacitor. The left half of the picture is the supply as-is (with choke input); the right half is the same supply set up as cap input.

http://i1243.photobucket.com/albums/gg559/Quagmire22/Choke%20vs%20Cap%20Input%20Supply_zpsnywzj0ww.p...

Notice that with choke input the draw is a smooth sinusoid. With cap input the draw is as you describe - sudden sharp pulses. The energy storage of the input choke smooths the current draw and also contributes to the very good regulation of the choke input supply.

Ait, Perhaps I'm missing something.  Imagine rectifier charging capacitors to 50V with 5mV ripple present. 

http://i.stack.imgur.com/BLGnf.gif

Capacitors are charged ONLY during voltage increase on capacitor.  This period for 5mV ripple (1% of 50V) is:

Arccos(0.999) x 16.6666ms / 360deg=0.12ms  

Charging current has to be huge (hundreds of amperes) during such short time to meet average current draw.  In addition to this huge current spikes rectifiers are not fast enough to turn off at the peak of the voltage conducting current for a moment in opposite direction to snap back to zero.  That creates extremely short spikes that large inductive caps won't filter and that will couple to any LC circuit.  Using "softer" diodes (faster switching - slower snap back) helps to reduce this noise (makes pulse longer).  There is a lot of switching noise from Linear PS polluting from 120Hz to tens of kHz

In addition to noise created by linear power supply huge spikes of current have also huge rms/average ratio causing big losses in transformer windings while high frequency component causes losses in the core (eddy currents, hysteresis).  You might filter these spikes with chokes but capacitor itself can be only charged during very short time (fraction of ms).

Ait, I understand that choke helps storing and releasing energy, but it won't affect charging of capacitors that has to happen in very short time.