Haskell it is
Haskell has impressive run time and memory performance; for example: comparing Haskell and Scala. I have been reading an online version of "Real World Haskell" and recently ordered a print-copy of the book.
I usually do most of my exploratory/research programming in Scheme or Common Lisp so using a different language is fun. Gambit-C Scheme does have the Termite package for concurrency but something more main-stream like Scala or Haskell seemed like a better idea. I invested some learning time in Erlang about a year ago but I think that Erlang is more optimized for concurrency over different computers on the same LAN rather than using many cores in a single server.