Bryston 4B3 vs Mac MC462 vs Pass Labs X250.8, OR... GRYPHON Diablo 300?


Hi,
Over the next few weeks I am organizing in-home demo of  three pre/power amps for my B&W 803D2's, and will purchase whichever sounds best.  I will be testing the following gear, which is based on what's available where live:
-Bryston B173 / 4B3-McIntosh C47 / MC462
-Pass Labs X250.8, if I can get my hands on one (will probably use the C47 pre-amp to test with this)
The Gryphon Diablo 300 is also a candidate.  I've seen some strong comments from others that Gryphon is in another league compared to the others.
My question is, barring what sounds best to me during my auditioning, in general to most people would the Diablo 300 really beat the others in my list?  And, are there any material disadvantages to sound quality considering the Diablo is an integrated vs the other choices?  I don't really care about having separates, but sound is obviously important.
Secondly related to the Gryphon, there is only one Gryphon dealer that is even remotely close to me.  Should that dealer cut ties down the road, or go out of business, does anyone know how I might go about getting service for the Diablo should I require it at some point?  Is that a valid concern?  There are multiple Mac dealers near me so that would not be so much of a concern.

Thanks in advance for any feedback....


nyev
Diablo's phono and dac are excellent, I just prefer tube phono stage, generally speaking. I also make recordings to tape from vinyl and like to go directly from phono to tape deck and not having to use tape outs, even Gryphon's, if I can help it.
Flemming Rasmussen, Gryphon chief designer, used to voice his equipment with master tape dubs of which he has a big collection. He knows how things should sound, oh yes he does.
I talked to couple of big time hard core tube audiophiles and they said that if they ever considered, as unlikely as it might be, transistor amp, that would almost certainly be Gryphon. This is a very high praise.
@ddafoe: Did you step up from a Pass Labs 150.8 ?

I went from a SimAudio 600i to the Pass 250.8 + XP10 stack.
The 600i was amazing and much better value than the Pass pair. 
After trying a couple preamps I ended up with the 250.8 + 740P combo and felt that was another level up from the 600i.   Since the 740P lists for the price of the 600i, I suppose that should not be a surprise...

I'm tempted to try a SimAudio 860a with the 740P to see how that compares with the 250.8, but they don't come up used very often.

@nyev, if you are in Canada, keep an eye out for good deals on SimAudio separates or the 700i integrated.   I've been extremely taken back by the sound quality and over-all quality of the two SimAudio pieces I've had in my system...  

ddafoeThank You for the follow up.  What other gear including cabling rounds out your system?  Happy Listening!
I'm currently using:

Roon on RaspPi, hifiberry digi+ pro,  iFi AUDIO iPower power supply
Shunyata ZTRON Anaconda Digital Cable
SimAudio Moon 380D DSD
Shunyata ZTRON Anaconda XLR
SimAudio 740P
Shunyata ZTRON Anaconda XLR
Pass 250.8
Shunyata ZTRON Anaconda Speaker Cable
Spendor D9s
and various Shunyata power cables

My Raspberry Pi based streamer seems out of place compared to the other components :)   Music still sounds amazing through it though and it works like a champ with Roon.

Cheers