That's a helpful idea - a quick overview of the distinct values, or even a count of the distinct values, for a field. I think you could get some way towards what you want by building a summary in a the reference model and then importing that into whichever model you're working on.
If you open up the model: C:\Users\Public\Documents\Monarch\Models\UserDefinedFunctions.xmod with the report "Classic.prn", and create a calculated field called Key, defined as Character and just set to be equal to Media. Then create a summary called KeyCount which just has Key as the key field, and count as the measure. Save the model with the summary definition, and return to your model. Now you can import the summary easily into your model, and as long as you have a field called Key, you'll have a quick way to get view you want.
You could also create a pre-canned summary with one down key and one across key, to give you a view of the spread of values across two dimensions.
Hope this helps,