Out of curiosity, what developer and dilution did you use? Out of the mainstream developers, I can't think of one that would give particularly dull results with HP5+, unless you are using it in a way not intended. As Matt mentioned, there are plenty of other things apart from speed rating that could be wrong, and it is well worth the effort to figure out exactly what it is that is not working for you as it should.

There is in principle nothing wrong with settling on an EI of 160 for your workflow, assuming that you scan only. I would rather understand how and why I deviate from the norm, though. That gives one far greater control and enables good decisions in difficult circumstances. While it may give the best results for your current scanning setup, there is something to be said for getting the best negative, and optimising your equipment and techniques around that. In future, that would enable a better scan from the same negative, or alternatively a better darkroom print. While Mark is correct in saying that keeping development constant, one may be able to get remarkably similar looking prints from EI 50 through 800, I must point out that you will definitely see deterioration in the shadows or highlights, depending on at which end you are. Whether that matters for a particular print is entirely dependent on how important those zones in the particular image are, and how well you can print a difficult negative. HP5+ captures easily more than 10 stops of dynamic range, but to get the extremes onto paper in a way that looks natural is not always that easy.