The old Ampex machines were nice, but the tube electronics were designed to be simple and easy to repair in the field but not audiophile grade. Sound beautiful but limited dynamic range and too much color!
This is not true.
The problem here is that when Ampex made their tube electronics was a good 40-55 years ago! They were amazing when they were new (many Living Stereo LPs were recorded on them) but have gone downhill due to age. If they are properly rebuilt they will take any solid state electronics ever made to task. If not rebuilt properly then I would agree that they can be colored- paper coupling caps perform well, but don't last for decades!
The transport is a different matter. It is arguable that the ATR was indeed the state of the art, but if you really wanted to make things go, find a way to make it work with the 351 tube electronics.