OK, you asked for the info, here it is.

The Fet Valve 600R Hybrid Amplifier $2949
The Fet Valve 400R Hybrid Amplifier $2549
Presenting the new AVA Fet Valve R series amplifiers, available in two models, the Fet Valve 600R (300 watts per channel) and the Fet Valve 400R (200 watts per channel).
Both offer absolutely unique engineering accomplishments; active regulated power supplies for each section of each channel. There are active 12V heater supplies for each tube, active 275V and 200V regulators for each plate of each tube and for the mos-fet drivers, and finally (and an audio engineering first we believe) active regulated power supplies for each power mos-fet output circuit, ten high speed analog high current regulated power supplies in all.
You have never heard before, at any price, the astonishing musical quality and control our engineering has now achieved. We offer simply astonishing bass range, control, and dynamics, open, layered, and emotional mid-range, and a top end that never stops, with no trace of glare, grain, or grit. Your speakers and your ears will never be happier.
Both amplifiers sound identical, you save $400 if you choose the Fet Valve 400R, if all you need is a very strong 200 watts per channel. The newest Exicon “double-die” power mos-fets are standard on both new Fet Valve R models.
Both amps use two ECC81/12AT7 tubes.
All new AVA products now include IEC power sockets and a ground lift switch to eliminate ground loop hum in complex systems.
Upgrade costs:
From any previous Fet Valve or Ultra amplifier in an AVA chassis: $1500
From a Fet Valve II series (including free shipping) $500
Upgrade includes new audio and regulated power supply boards (already done in Fet Valve II series), new output mos-fet configuration, new output decoupling boards, regulated output transistor circuits, and double die Exicon mos-fet output devices as required. The output configuration is different than that of all previous models.
Note that we privately built a few Fet Valve II versions without the regulated output power supplies because we had these new audio and regulated power supply boards (for everything except the output mos-fets) done and were at that time not sure at all about being able to complete a reliable full regulated output circuit short term. That is the reason for the lower cost upgrade and free shipping for those that did the Fet Valve II series upgrade (cost was $999). If these owners want "the rest of the story" they won't pay any more than anyone else.
We will have the new output decoupling boards available in about three weeks so wait until then before considering this upgrade.
Best regards,
Frank Van Alstine