Thiel Owners

@thoft, the original Krell FPB's ("Full Power Balanced") are designed to work best through their balanced inputs, though if you wanted to direct connect to a high bit, high output DAC the RCA inputs might have an advantage to avoid bit stripping. The latter FPBC's and FPBCX's don't even have RCA  inputs; only XLR and CAST.
As far as using an intergraded as a pre, well I suggest using the KISS approach. Your just introducing more potential noise and failure prone parts.

I think focusing on doubling is somewhat misguided.  If an amp is stable and low distortion into 2 ohms it should be fine.  How much power can it put into 2 ohms?  An amp that can put 300w/ch into 2 ohms can put 150 into 4 ohms and 75 into 8.  Whatever it can put into 2 ohms is what matters rather than doubling.

With the 3.7s it's hard for me to imagine they need a huge amp.  They're 90db sensitive.  (Stereophile measured 90.7.)  2 watts for 93db, 4 for 96, 8 for 99, 16 for 102, 32 for 105, 64 for 108, 128 for 111, 256 for 114.  I'd be shocked if these can get anywhere close to 114db before exceeding their physical limits.  The fairly inexpensive amps I have do the first 30 watts in class A.  I'd bet that pretty much all of my listening is in class A.  I worry about bottoming out the drivers a lot more than the amps.  

@jon_5912, That’s not quite correct. They’re spec’d at:
90 dB at 2.83 V 1/m
not
90 dB at 1Watt 1/m
You need to drop the sensitivity by 3dB for each halving of impedance below 8 Ohms.
I don’t know what amp you are using to drive which speakers, but it’s not uncommon for an amp to halve it’s Class A output as it doubles it’s output with each halving of impedance.

Even so, it's 32 watts for 102 db.  I appreciate the benefits of extra power but the Krell FPB300 puts 600w/ch into 4 ohms.  

64/105, 128/108, 256/111, 512/114.  I'm skeptical, do you buy Thiels because you like it loud?  They're magnificent with unamplified music at reasonable volumes.  I tend to doubt you can have the best of everything in one package.  Wouldn't drivers that can play crazy loud need to be built differently than ones that are optimized for detail?  

The luxman is fully restored and completely rebuilt with a new transformer boards and etc. it is basically new. I have confidence that “failure prone parts” and “potential noise introductions” are well resolved and don’t even exist.