Maybe try a R2R Dac to the RME, such as a Denefrips Ares ll. A reviewer compared it to the RME along with some other Dacs to the Ares ll, and he preferred it to RME.
Take the reviewers opinion (and mine for that matter) with a grain of salt, as just what it is, a opinion.
Take the reviewers opinion (and mine for that matter) with a grain of salt, as just what it is, a opinion.