I once had a SF Power 2, which while not being Mono, it did output out a good 110 watts per channel. A massive beast, weighting 115 pounds. The sound was excellent running my Gershman X-1s and SW-1 subs with authority and plenty of volume. Nevertheless, I felt that as with other tubed amps, there was an issue with the bass being a bit loose.
in clear contrast, I had the Nakamichi PA-7 MKI, which outputed out 200 watts. Which this amp, the bass was outstanding with immense sense of slamm, much better control.
If you are worried about bass, then, I am afraid you are looking in the wrong tree to get some satisfaction. From real life experience, I say get a slamming SS amp. You will never, ever look back. For tube flavor, you can get an excellent tubed preamp. This is the best compromise I can find.
PS: I have long ago sold the PA-7 and the Sonic Frontiers Power 2, and I am presently running a tubed preamp+small SS amp mono set up. I still remember the sound of the PA-7 fondly. One honey of a SS amp, with great voicing and slamm.