right now, i am using a arc pre 650 ohm to a bryston amp 20k ohms to very good effect. impedance matching was not an issue. i had a sf line-2 briefly many years ago. paired with a krell amp presented no problems.
more important i think to consider in your search for an amp is speaker and room size matching. you want to pick an amp that's a good match for your speakers and is able to drive your speakers at levels you like in ur size room. after that, its personal taste.
in kalman rubinson's stereophile review of the SF line-2, he matched it with a mccormack dna-1 and sim cleleste moon w-5. i believe he used the line-2 (later the line-3) as his reference, so you can look for his reviews of SS amps in the stereophile archives.