While you can use the SF-2 as a preamp, and I think there are a few club members that do, most people don't. It does not have a tube circuit and does not sound the same as an F-1X or F-2B. The SF-2 is a wonderful tone shaping tool, but it's not the same thing as an F-1X or F-2B.
As for power amps, club members use a wide variety; but it does seem that QSC, Crown, Crest and Stewart are mentioned most often. Personally, I use a QSC PLX 2402; which in my view is a good combination of quality, reliability, power, and weight.