I never heard the HR-X but changed from a Basis Debut Gold with Graham 2.2 to an SME 20/2 with Triplanar VII. The SME/Triplanar was a BIG improvement. Much more resolving, quieter blacker background, greater transparancy, better dimensionality, better dynamic shading, etc.
The build quality on the SME is amongst the best I've seen. Based on talking with some very knowledgable people, the consensus was that SME is definitely superior to VPI.