The SS8 speakers are rated by Salk as 4 ohm and he recommends amps from 100 to 250 w/c. Your S550i, rated at 200 w/c at 8 ohms and 400 w/c at 4 ohms, should drive those speakers without any trouble.
I've heard them driven by 125 w/c amps, without an apparent problem. I've also heard them driven by larger amps with as much as 300 w/c. They easily handle high power, but they don't require it.
What do you see that makes you think they are a difficult load?
If you are interested, you might phone or email Jim Salk and ask this same question.
