Lots of things to discuss, but I have little time. Here is what has worked for me with the LDR pre from Tortuga.
ACA Nelson Pass Amp Camp Amps, 5 watts, current set up in my system with open baffle Tang Band 1808's works well for me.
First Watt F6 was great, no issues
Declare 84 tube amp, not good. More of a power issue I think.
F5 great amp and combination
ATI 1502, it was fine, but I think this amp is more for theater systems. Sound was just ok, lacked clarity and depth
Fleawatt 3116 Chip amp was great. No issues driving OB's, Klipsch 2.2's, Zu Cubes, DIY to good levels and good sound
Fleawatt 3116 mono's, good
DIY 1625 Mono Block tube amps 55 wpm, wonderful sound