I had listen to both 50SE and 5SE, before deciding to go with 5SE. Reason being the 5SE is slightly rounder and smoother, while 50SE is super transparent but just a bit too 'in the face'. Personal preference.
To summarize my experience:
Aurios are well engineered isolatio device, at used price of $150, they are worth it.
However, placing Aurios directly under 50SE is not as good. I have a little 3M Bumpon rubber on top of the Aurios to decouple so I don't get a metal-metal contact.
The rubber feet of the 50SE cause the sound to lack transparency. Whatever you do, as long as the rubber feet are bypassed, the sound will improve.
Sorry, not to brag, but the 50SE benefits not just from isolation, which already discussed by above posts, as a tube unit, and very huge and heavy, it needs the vibration (for example, feedback from speakers and room) to be drained away. The best such vibration dissipation device is carbon graphite based design (Black Diamond Racing is not the best solution, because of the heavy core inside, it stores too much energy, which it then releases those stored energy slowly over time, smearing the microdynamics).