High-performance computing / MPI

I'm contemplating purchase of Mac Pro (dual-quad core Nehalem) with a view towards development of parallel computing applications to genomics and general optimization. Curious about suitable MPI and parallel computation environment---OpenMPI appears to be included with XCode. Would compiled mpi code need to be submitted via XGrid? Would a dual-quad Nehalem-based system support 16 independent parallel processes? I'd be curious to read about others' experiences with setting up & utilizing similar systems.

Message was edited by: duffmanscriblerus