Seadweller,
You should also keep in mind that eficiency ratings are only taken at 1kHz frequency.
Bass and speed is what you won't get from Cary.
As to 2...5 Watts even onto sub-100db/w/m efficient speakers the amp will only 'see' normally vocal frequencies.
As you've mentioned 250w/ch onto 99dB can only increase speed and bass and wouldn't do anything wrong.
You should also keep in mind that eficiency ratings are only taken at 1kHz frequency.
Bass and speed is what you won't get from Cary.
As to 2...5 Watts even onto sub-100db/w/m efficient speakers the amp will only 'see' normally vocal frequencies.
As you've mentioned 250w/ch onto 99dB can only increase speed and bass and wouldn't do anything wrong.