It's hard to respond to your question without knowing what kind of music you like, and it would help to know whether or not you've got an HDCD player. Here are a few of my favorite RR recordings:
(1) Strauss, Ein Heldenleben, Oue, Minnesota Orchestra, HDCD. A great performance of a great work, fully exploiting all the resources of a large orchestra as only Strauss could. Superb HDCD sound.
(2) Felix Hell, "Organ Sensation," Liszt, Vierne, Guilmant. This gets my vote as the ultimate audiophile pipe organ CD. If you want a real lease-breaker, if you want to test the depths to which your subwoofer can reach, this is the one. Terrific HDCD sound, with bottom end that will take your breath away.
(3 & 4) Nojima Plays Liszt, Nojima Plays Ravel. These precede HDCD, but don't let that stop you. Wonderful performances of great music by a master pianist, captured in magnificent sound.
(5) Eileen Farrell Sings Torch Songs. The first song here, "Stormy Weather," is the most perfect recording of a great vocal "standard" in the technical sense that I've ever heard. The vocal is backed up by a "just right" jazz combo, and the sound is impeccable: the group is right there in front of you in your listening room. (This song is also on the RR Jazz sampler.) This one is also pre-HDCD. Truly a reference recording.
Hope this helps. Happy listening.