Good suggestions by Charles, as usual. A couple of caveats, though, regarding the First Watt F6 and F7.
Their gain is particularly low for a power amplifier, at only 14 db. That will be problematic in some applications, especially if vinyl sources are being used and line stage gain is low. Also, the F7 has an input impedance of only 10K, which will be a problem for many tube preamps.
Basically, I would view the Dynamo as being more versatile than the F6 and F7 in terms of compatibility with upstream components. While I would expect the F6 and F7 to have greater versatility than the Dynamo with respect to speaker compatibility, due to their greater power capability and also their presumably much lower output impedance. With the S.I.T. amps being more comparable to the Dynamo in the respects I've mentioned than to the F6 and F7.
Best regards,
-- Al