Krell FPB 300cx vs Jeff Rowland 501's?

Chances are the Krell will mate very well with Capri, as Capri has very low output impedance: the manual lists 40 Ohms single ended and 80 Ohms balanced, making it quite compatible with most amps on the market. Other Capri specs and manual at:
http://jeffrowland.com/CapriPreamp.htm
Guido

The Rowland preamps are very quiet, which is a crucial performance parameter, and especially quiet when run with balanced equipment. As Guido notes, they also feature a very low output impedence, meaning they can drive anything (I was able to drive my darTZeel amp with a 50 Ohm BNC connection - my Coherence II has a 50 Ohm output impedence - but ultimately decided on a balanced connection). Finally, the ones I have personal experience with layer space and have the musicality of the best tubed preamps (which says a lot). In short, a Rowland preamp will always be competitive with the best solid-state preamps and would presumably work nicely with the Krell.

I even prefer the JRDG Capri to my ARC Ref 3 for driving my JRDG 312 amp. To my ears, Capri yields greater top to bottom extension, linearity, harmonic complexity, authority, macro and micro dynamics. Staging and imaging seem to me comparable between the two.

Wow! That is quite a statement that you prefer the capri to the ARC Ref 3 considering the Capri is about $5,000 cheaper on the used market. Was your preference given with or without the Rowland A.C. filter?

My preference is for the Capri directly plugged into the AC, without PC1 Power Factor Correction device. I am planning to test the PC1 on Capri once again in the near future. I have tried 3 PCs on Capri this far:

PAD anniversary -- oddly, I did not like it in this application. . . some unwanted warmth in the lower part of the spectrum, slightly unclear bass, and a feeling of harmonics in the treble region 'disconnected' from the fundamental. Pad Anniv works very well on my X-01 Ltd and on ARC Ref 3 instead.

Cardas Golden Ref -- Good wire without too many flaws. . . not the ultimate extension, and some very slight raggedness at the top.

Shunyata Anaconda helix Alpha -- My preferred PC of the group. . . The most extended and apparently linear. One criticism that has been made by some to Anaconda is to yield slightly softened transients. . . but I still enjoy it very much.

Hope this helps. Guido