I am sure these 8" subwoofers could compete well in bass per given floorspace
It was actually Tom Nousaine who challenged subwoofer manufacturers many years ago to provide more bass for less floorspace, and hence the birth of the TN series in the mid 90's.
However, the 8" subwoofers would be at a disadvantage in terms of maximum output and absolute low end frequency response due primarily to size and displacement.
Anyway, if discussion is about subwoofers in the low $200 range, then none of the STF are applicable.
Sometimes very good values can be found on the used market too, but it is not very common to see the more expensive used subwoofers dip into the low $200 price range discussed here.
P.S. Thank you for the kind words about the STF-1, John! I am glad that you liked the sound quality.
Sincerely,