First Watt J2

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. 

Thanks for all the input. My current (integrated) amp for these speakers is a Sophia Electric Baby 10wpc push/pull version and they sound decent, especially vocals at lower volumes. Looking for something to upgrade and add more "body" in the mid/upper mid bass range. Definitely open to tubes as well. This is a second system so trying to keep the budget around $2K used.