Would that mean that you listen at low volumes only or that the 5.5's are sensitive enough to go loud without compressing/distorting with only a few watts ? I plan to use the with an Aleph 3 which as you probably know is a 30 watt per channel (60 into 4 ohms)transistor SET.
I'm not an expert in this. You can ask others. I live in a townhouse. The speakers pictured below in the other threads are located in the living room which also has a high ceiling. It gets really loud. I can turn the volume all the way up to 10. The onken enclosure i have isn't optimized for the DCA. Volume capacity is only 13.28 liters. Planet10 mentioned it should be around 20.
I'm a fan of Nelson Pass amps too. My other project is an F2 car amplifier to drive a DC Gold 9.5R single driver.
My listening room is rather large, about 500 square feet with 11 foot ceiling plus open doors into the rest of the house. The Gallos are recommended for medium sized spaces and I wondered whether the 5.5's suffer from this limitation
Mine is rather big too. ceiling is around 20-30 feet high and living room isn't enclosed either. And don't forget the subjective factor. What may be just right for me might be different for you.
You can also try DrD's BIB' enclosure for the DCA5.5M. It can go down as low as 29hz.