First of all, it's always a pleasure to converse with someone who wishes to take their art to a higher level and improve their skills.
Now then, you ask a very pointed question: What makes a compressor high end?
This is technically an easy question to answer.
- Preserves the audio integrity of the program material.
- Imparts a desired control of dynamics on the signal.
- Does not introduce unwanted artifacts (eg. unpleasant odd order harmonic distortion) on the program material
- "improves" the source material by thickening the sound or imparting a more pleasant tone.
There is more than one type of design for you to consider. REad this, an audio compression primer
first to get a basic understanding of what your chosen unit was designed to do.
And now, to understand the circuit design characteristics of various compressors, I'm sure you've read our discussions about VCA, Vari-Mu, Optical compressors etc... Read this- seriously, click on this and read every word.
Now, as for recommendations for the types of program material you have described for your compression applications, I think you wish to have something that isn't too aggressive but imparts good smoothing and leveling and won't radically alter the tone of your source material.
My strongest recommendation is an LA2A. Or a CL1b. Both are tube designs, but you should also consider solid state designs which can impart little to no harmonic distortion.
I'm awaiting Fletcher to weigh in here now with some sage advice, now that I've provided you with a solid foundation to begin your research with.
And speaking of that: Do your own research! Don't depend on what I say. Find out what works for you. Book some time in a well-equipped recording studio and INVEST some of your money in trying out various compressors until you find what suits your needs.
Best of luck!