Resolution Audio Opus 21 questions

My experience parallels J evege and Gnobber. I found running the Opus 21 directly into my amp (BEL 1001) to sound very clean but flat and not as involving as running through my preamp (deHavilland Ultraverve or Audible Illusions 2C). I too had hoped and prayed that it would sound better direct, and even now occasionally hook it up that way in a fit of wishful thinking, but every time I do I go back to the tubed preamp. I also got a DNM DIN to RCA interconnect to bypass the internal volume control but, unlike some of the others posting I hear almost no difference between the DIN and RCA outputs- as a matter of fact I find the DIN output to sound a little less smooth, but this may be a function of the interconnect itself (my RCA out interconnect is an Audience Au24, which, as noted, is available in a DIN to RCA version for more $$$). As an aside, does anyone have any experience with the RA integrated amp, which connects directly to the cd player thus eliminating the need for an interconnect as well as a separate preamp??