krell FPB300 or jeff rowland model 7

The FPB sounded pretty good initially to me but after sitting with it for a week or two the "Krell" bass was just not there in comparison to the KSA series or even the Pass Lab X series. It has a high number of small capacitors opposed to the few larger beer can type that made it quick on transients but thinner on bass qualities. That was my observation pretty quickly so I sold her her.
Then went on to the Pass Labs X-350 which sounded much more in command as well as bass beefier until I heard the Parasound JC-1 monoblocks and there was NO comparison. I have those to this day and doubt there is much better at even twice the price.

Classe CAM 350's ain't chopped liver either.

what about mark 332.5?

332.5 is another really good amp. I heard the 331.5 which is approx 80% the 334. Personally I would rather have the Levinson than all the ones you mention. I have owned the 27, 27.5, 29, had the 331.5 in my system, and a buddy has the 334. The 334 bests all of the other ML amps I have heard.

There are better amps you can get for the price of used FPB300 (~$2700). Pass X-250 is one of them. I had a chance to compare them side by side in my system - Pass is by far much more transparent, open on top, soundstaging is much better etc. They are just not in the same league.

Interestingly, the X-350, doesn't sound as good as X-250 IMO.

The other amp worth investigatong is Cary CAD-500MB. You can get one used below $3k if you are lucky. It is even better than the Pass X-250, and MUCH better than FPB-300 or X-350.