which amp is the most transparent?

I have four complete systems, including one in the basement. They are all fed by a computer which has two hard drives filled with my favorite music. This is music I have accumulated over my forty plus years as a music lover.
This setup allows me to wander around the house, work on projects in the basement, or retreat to the main listening room and focus on the music.
I am a music lover as opposed to an equipment lover. Sound is what you hear, music is what you feel. If I do not feel the music, the brand of equipment the sound is emanating from does not impress me.
The subject of this discourse is my bedroom system, and not even the master bedroom. I have a wife and she likes to look at that thing called television.
If I have given you the impression I am on an unlimited budget, I apoligize. I am simply a senior audiophile who has accumulated a lot of equipment over the years and one of the things this discourse is about, is achieving maximum bang for the buck. While I am an electronics technician which certainly helps in modifying equipment, it is only absolutely essential that one be able to solder in order to get maximum bang for the buck.
The 60's tube sound is the ultimate sound for me. This sound is synonymous with the 60's juke boxes. The music of that decade can only sound exactly as it sounded at that time by extracting the 60's tube sound from whatever equipment you may use.
I began my quest with a Marantz Super Audio CD8260 and a Conrad Johnson PV10A. To make the PV10A quieter I replaced the electrolytic caps with "Black Gates". To get the tube sound I was seeking, I replaced the tubes with 60's NOS tubes. Since these tubes are essential in obtaining this sound great care must be taken. I chose "Brent Jessee Recording"; they took the time to discuss tubes, from the cheapest to the most expensive.
I needed a good tube amp (so I thought). Audio Research certainly came to mind, but I could not squeeze Audio Research into my budget. I had read good reviews on "Musical Design" amps, and these amps agreed with my budget. Although the D-75B suited my budget and power reequirements, it was solid state.
I called John Hillig at "Musical Design" and after discussing what I was going for, he told me that nothing less than the D-75B Signature model would be transparent enough to allow the tube sound of the CJ to pass through and come out as the CJ tube sound, and if I didn't like it I could send it back. The "Signature" model has more expensive parts including "Black Gates".
Although the sound of the PV10A had improved tremendously, and even takent on a new personality, I was a long way from the sound I wanted. I needed the right amplifier. The D-75B Signature was on its way.
It always feels good to open that box when audio equipment arrives. The D-75B looked like a business piece of equipment with a lot of heft for its size; a lot of premium parts in that enclosure. After I installed the D-75B, it was love on first CD.
At this point, let me clarify some things that seem like contradictions. I have achieved the ultimate 60's tube sound with a solid state amp. No, this amp is not tube-like. This amp is so transparent that it allows the exquisite beauty of the 60's tubes to pass through and be heard. Now I know why those tubes are so sought after and why some of them are so expensive.
I have the 60's tube sound without the noise and distortion that went with the territory at the time. I have that sound with today's "black as midnight" background.
Congratulations, it sounds like you have a system you are happy with, enjoy! That leaves us with the title of your post, a question that is never fully clarified in the body of your post. Which amp? Transparent compared to what? Please explain further.
musical design amps and pre's are among the finest sounding components out there....you obviously already know that.
Kudos to you!

You knew what you wanted, and you carefully chose equipment to get you
there with a fairly modest expenditure, and apparently with a pretty direct
path to your goal.

It makes me envious. :)
"The "Signature" model has more expensive parts including "Black Gates"."

That's good enough for me....tranparent with a capital "t" atleast that's my experience with "Black Gates"
Orpheus10, FWIW, tube amplifier designs have evolved a lot since the 1960s, although the CJ amps (for the most part) tend to have a lot of the textbook-style circuits from that era.

One area that tube amps have really improved in is the area of transparency. They have done this without the often-common tradeoff of added brightness. Although Black Gate caps can be helpful, they are by no means the deciding factor- there are new topologies and other materials that make quite a bit more of a difference.

IMO, price is not the most important variable either.