Thanks for a detailed opinion. I share your thoughts on how they sound when powered by a mid-fi AV receiver, I did try connecting SFs to my home theater receiver (an older Denon AVR 3806), they sounded dull. I have had the SF 2.5s for a week now, and yes they are very smooth on the top, the Hales were a bit bright. The other difference I noticed was the midbass (like the lower cello notes) pretty much didn't have any heft in Hales, the SFs do and of course as you mentioned the SFs are much more dynamic when compared to Hales
The Hales are definitely superior in the bass department but again the Hales go down to 33Hz where as the SFs go as low as 40Hz.
The build quality (and place of manufacture) are not the same as other SFs, but I think for the price, the 2.5s are great speakers.
As for the plastic like vibrations, I didn't hear that in my speakers.
So SFs with better mids and highs, for me are an upgrade from Hales :-)), the other thing I had in mind when I bought the SFs was the difference in power needed to drive the speakers. Hales are very inefficient speakers (and a sealed box design), when I auditioned the SFs, they were being driven by Primaluna Dialog Two (38 watts) and sounded gorgeous. They sound great with my DK Design VS1 MKII but I think I'll be moving to a tube integrated soon.