Many Thanks to both responders
Since then I have made some changes to confirm the problem: moved the Stratas to a different and much smaller room with wood floors, and connected to an Onkyo TX8160 receiver (80 wpc into 8ohms plus an Onkyo CD 7030). In addition, I have connected my old Cambridge Soundworks Model SIx speakers to the original electronics I described in the first post. Results for the Stratas are the same; tin-can sound and only running the receiver wide-open produces a normal output volume. The Cambridge Model Six (connected to ARCAM P49 and Sonus Veritas Genoa pre-amp) sound exactly as they should, running at 12:00 volume setting produces full, clean output volume.
I read a few reviews of the Stratas before purchasing and did not find any indication of the problems I am hearing. Everyone loves these speakers right out of the box, and no one complains of needing extended break-in time. Although, the optional Gallo subwoofer DOES require considerable break-in.