The current power supply upgrade for the OR5 is the DYNAMO. This supply is AC powered and Hynes-regulator based. Sells for $699.00. Many customers say that the power supply is a bigger upgrade than the OR5 or the Synchro-Mesh makes.
The other significant upgrade that Empirical offers is the BNC-BNC coax cable with RCA adapters. This cable is currently unbeaten in the market and only $250.00.
The OR5 can also get the "OTL" mod for $150, which removes the output transformer. This reduces jitter even more. It helps to have a DAC with a Coax input transformer on it.
If you have the OTL, Dynamo and BNC-BNC combination, I don't believe the OR5 has any competition.
Steve N.
Empirical Audio