Is there any value in atypical graduate degrees for CPAs?

I've been starting to think potential options for advanced degrees within the next few years, and am looking for some info/input on people's experience with atypical graduate degrees for CPAs – I'm closing in on two years in tax at a boutique firm currently. I had a decent GPA (3.7) in college but went to a non-major state school so getting into a top-15 MBA program is out of the question, and general concensus on GC seems to be that outside the cream of the crop MBA's aren't worth it. My experience in tax has been fine so far and I've been highly rated on all my reviews, but I'm not quite sure that I'm ready to commit 100% to tax, so I'm a little iffy about trapping myself or potentially limiting future options by doing an MsT. Does anyone else have any experience with or know of someone in a similar position who has gotten value out of a tangentially-related graduate degree? Something like economics, financial engineering, statistics etc, or is the choice more realistically MsT, MBA, or bust?