The new Fet Valve product line for the preamp, DAC and power amp has required a major change to the steel chassis. If you will notice on the preamp, DAC and amp, the old lighted power switch is gone, replaced by a new on/off switch with a LED as a power "on" indicator. The chassis requires lots of new holes and configurations to accomplish this, and would be impractical or almost impossible to drill/grind/saw in existing sheet metal.
Also, all of the external panel fasteners have been removed from this line for cosmetics, that also requires changes to the steel chassis.
The new Fet Valve line is not a line that replaces anything, it is an addition to the existing lines. Older products can't be turned into Fet Valves (at least having the new thick faceplate and new switch), but new Fet Valves can be put into older chassis. Kind of like a diode, it goes one way, but not the other.
There will not be an "EC" version preamp in the new Fet Valve line either as the tone controls are not possible with the Broskie/Kayser circuits.
Wayner