I think the Fisher ST series were produced after the original owner sold, and most speakers produced after he sold weren't very high end and some were terribly cheap...the quality really slipped after the original Mr Fisher sold. Don't really know much about the ST series, however! Second, Fisher speakers aren't very sensitive from what I remember and can tell from looking up specs...so you may need a lot of power to make them sound good...
And yes, it would NOT make any sense to use these as surrounds and it would make even less sense to buy a dedicated amp for your surrounds. Surround content won't have a lot of bass either!
I guess the question is, do you want to spend hundreds of dollars on Amplification for speakers that could be replaced with more sensitive speakers for hundreds of dollars!?