Just to add some observations. The Crane Song Avocent may be an older device, but I cannot see that it uses op amps of any type (unless they are to be used as assists in power supply or other circuits. As far as I can tell from images, the Avocet uses fully discrete circuits (as it is labeled "Discrete Class A Studio Controller".
It's interesting that you did not like the Boulder. I have never heard it, but I believe that it uses bipolar audio stages (as opposed to FET based). Each has it's own sound, but bipolar is usually cleaner sounding.
I have read that BAT equipment is nice, but it does sound a little dark. That particular BAT preamp looks to be a fully solid-state FET based device (no tubes, which is unusual for BAT). It has a seriously massive main power supply, which is great for bass and midbass response. However, I don't see a lot of smaller capacitors and I can't identify where the gain stages are. Anyways, interesting product.
brianlucey - I suspect many of your responses are due towards personal taste as well as system synergy. Like everyone else here, welcome to the journey of buying and selling. It has been a journey for me as I have learned what types of equipment I like and what I do not like. Many people will agree with my results, but many will also disagree with their own preferences, lol.
For comments on "pro equipment", there are different levels of pro equipment. Brian is obviously playing on the top tier of equipment. If you look at "common pro equipment", you will actually find a lot of junk, such as anything Behringer (etc.). Lot's of mid-level stuff. You won't get to the top level until you start getting stuff that uses discrete op amp modules (such as MM-99 or JFET-993, etc.). This is very expensive stuff.
Bryan - maybe you might look into whether you like more of a FET based sound or a bipolar. The bipolar are usually cleaner (less distortion), but they can also be somewhat clinical/sterile at times. The FET based circuits do add a color or texture to the sound which can be very pleasing to some people. The Boulder 1010 is bipolar. I suspect the Crane Song may be FET based. The BAT vk-43SE is definitely FET based circuit. Maybe look into one of the Pass Labs preamps (such as XP-30). Pass likes to use discrete FET based audio stages.