Amp suggestions needed

Wood, you have three great amps listed but I don't thnk that the BAT or McCormack have enough power to properly drive the Duettas. My choice would be to use (2) McCormack (or BAT) amps in bridged mode.

You might also consider a used Sonographe SA-400 amp - I used one with my Apogee hybrids for years with great results.

I have the Duetta Sigs., it is the impedance more than the power you have to worry about. My Tandberg 3026a and Meridian 605s are both rated at 150 watts but the Meridian would drive them and the Tandberg would not. I don't think bridged is a good idea because bridging an amp usually limits its ability to handle low impedance loads. The hybrids are another case entirely, much easier to drive. The original Apogee , which was bigger and had an even worse impedance curve, worked very well with the Classe 25 watt class a amp. The tube units with transformers should work, I have never used them, I did use a custom hybrid with mosfet outputs that had about 100 watts and it worked fine. Look at power supply design and not rated output.

I would consider those b&k m200 sonata monoblocks with mods;
should drive without a problem and be on the warm side;this has been by experience driving merlin 4b+'s with these amps.