I too own an MP-500 it currently rides in an Origin Live Silver,I have to agree with Normansizemore, it is a very engaging cartridge that throws a wide believable soundstage that frequently extends well beyond the speakers boundaries.
Similar to Slowhead I run mine into a fixed stage as well,43db/47k and I'm getting phenomenal results.I am in the process of having my phonostage's MM section allow for variable loading, to see how much further this cartridge can improve.
when I purchased the 500 I wasn't expecting this level of refinement and transparency,as mentioned it's not the fastest nor most dynamic, it is truly an enjoyable cartridge.