First Watt J2

I think that you've interchanged the mentions of the two amps. The J2, with its 0.4 ohm output impedance, behaves pretty much as a voltage source. The F2, with its 15 ohm output impedance, is the amp that behaves as a current source.

But to answer your question, while I have no experience with these amps, I would approach this endeavor with caution. See the following paper by Nelson Pass, about current source amps:

http://www.firstwatt.com/pdf/art_cs_amps.pdf

Note the many examples in which various passive components (resistors, capacitors, and in some cases inductors) are paralleled with the speaker to optimize sonics, with the values of those components depending on the particular driver. And note this statement in the conclusion section of the paper, especially the reference to "electrical networks":

Current sources and amplifiers with low damping offer interesting possibilities for improvement with these [full-range high-efficiency] drivers but they require considerable work to get the enclosures, electrical networks and acoustic environment just right.

Best regards,
-- Al 

Why not buy an actual tube OTL like an atmosphere???

Al, thanks for the input, as always. My remark regarding the J2 as being a current source amplifier was solely based on the power output specs of 25w@8 ohm and 13w@4ohm vs. the F2 specs of 5w@8ohms and 10w@4ohms which seemed to imply a voltage source amplifier, e.g., doubling the power as the impedance is halved. I completely missed the (significant) difference in the amplifiers’ output impedance which seems to be more in line with what Nelson seems to recommend for the type of speakers in question, higher the better all other things being equal. Interestingly, I experimented with what he had suggested in that paper by adding different value resistors in line with the speakers and running them using my Adcom 545 amplifier. The results were not satisfying. The added resistors seemed to veil the sound and made the speakers quite dull sounding.