Responses from laaudionut

Are Pass Labs XA60.8 mono amps enough?
I had the Pass XA60.8's driving the Focal Sopra II and they were more than enough to make them sing with no strain at all. Pair them with a tube preamp to tame the slight brightness that Focal's are known for.  
Used tube preamp $2-3K
Any of Aric Audio's tube preamps would be a great investment either new or pre-owned. Most of them have adjustable gain which is helpful with amp pairing.  
Keep McIntosh C2500 pre-amp or upgrade to C12000?
I second the Aric Audio Motherlode suggestion. I had both the 2300 and the 2500 prior to the Motherlode...the difference in performance will make you question Mac and high end audio (read; exorbitant cost structure) in general.  
Warm, yet detailed tube preamp
Aric Audio Motherlode II should be high on your list of considerations. Call him to discuss exactly what you seek...his customer service is as legendary as his tube gear.  
Speaker Slip Covers
I have a pair of TAD Monitor speakers and I went on to Etsy and found a woman out of Bulgaria who makes very high end custom covers for stereo equipment and speakers. You provide her with the dimensions you need or with the make and model of gear ... 
Non-fatiguing speakers in $10K range?
Not on most radars, but you might want to do a little due diligence on Canadian made, PSB Speakers. I own TAD's now, but my first pair of reference speakers were the PSB Stratus Gold's, and they were nothing short of fantastic and extremely pleasi... 
PSB Stratus Silver
I should have noted that a few years ago I sold my pair of PSB Stratus Gold's for $1100 as my reference for $800 price suggestion. Original owner and mint condition.   
PSB Stratus Silver
I strongly second the recommendation to reach out to Aric at Aric Audio. His tube gear, and the Motherlode preamp in particular, are world-class and a fantastic value.   
Tube amps under $7500
@hickmore, I assure you, you are heading in the right direction with Aric. His gear and customer service are beyond compare! Best wishes for audio bliss!  
Tube amps under $7500
If you have not reached out to Aric at Aric Audio, then your due diligence is not complete.   
40+ watts SET, cost is not a problem
Reach out to Aric at Aric Audio for his take. Perhaps something bespoke is what you seek and what he can likely deliver.  
TRL DUDE preamp
One can dream, Bob(sigh)...    
TRL DUDE preamp
Bob, Audio and the enjoyment of music should not be a hassle. I will do you a selfless favor and take The Dude off of your hands. Brian  
The new Coda S5.5 amplifier: It's a "Petite Beast"!
The Accuphase may be a fit for the S5.5, but if you feel that it fails to live up to the performance of the Coda, I would also enthusiastically recommend reaching out to Aric at Aric Audio. I have the Coda Model 16 mated to the Original Motherlode...