Replacing my Krell FPB 600 amp with a tube amp

So here is my bad take, overall. 

The Krell's that I remember in the day of the B&W Nautilus were cold and analytical as hell. Having heard the top of the line, 5 amplifier setup with Krell crossover and B&W Nautilus speakers I was never wowed, but if you were that's cool. 

If you want to keep that, you want old ARC. If you want something musical and juicy you want Conrad Johnson. 

I also remember the Nautilus, a bit cold and analytical yes - I preferred the Dynaudios for that reason. But I felt it was the speakers mainly not the amp. 

@tattooedtrackman - It appears that your ARC Ref 6 preamp has two variable outputs and one fixed line out for use with a tape recorder.
You pay your $14,000 but you get what you pay for!

I think @rcprince may be right. I have gotten very good results from VTL MB450III mated to my ARC Ref 40 to drive my Q3s. The variable damping factor on the VTLs allows you to optimize for the speakers you are using and address the issues @almarg raises. The VTLs are also very robust with super reliable automated biasing. Even a full on tube failure is handled with aplomb. If you do go the VTL route however you are advised to buy from a VTL dealer as they can be sketchy on support if you don’t have that relationship. Finally make sure to connect the pre and power amp with balanced interconnects.

dweller.... That is correct... I will tell you that this ARC Ref 6 is so awesome in sound that it will very likely be my very last preamp. You must hear it to believe and appreciate it.