Krell FPB300CX or FPB600 to my B&W N802

Hope you can help me. Who is sounding best Krell FPB300CX or FPB600 to my N802.
Both are secondhand with a good price.
My music taste are blues, jazz and rock/pop.
I have owned Krell forever starting with the KSA 250, then the FPB300, the FPB600 and now the FPB 600MC mono's. I had the old B&W801's with my Krell 250, then the 300. I would spring for the 600FPB because sonically it is better than the 300FPB and the lower efficiency of the B&W will love the extra current. The CX version of the Krell amps refine the sound a little more and give more power from the same transformers, but how they do it, I do not know. I really enjoyed the bass control of the Krell on my B&W's. I have Wilson MAXX now and love them best for the dynamics and detail. Good luck, you probably can't go wrong with either.
My gut feeling:

The 300cx is based on the 200 which was not in the same class as the original 300 and 600.
With the cx you cannot use an aftermarket powercord, which can make a huge improvement. If it were me, I would buy the 600 and an aftermarket powercord. (My preference is the Pure Note Sigma.) You will probably get a better sounding amp, plus a lot more power.
The only downside is the weight of the FPB600.