Tom, the jump to the DR-6 was a big improvemnt over the 30. Better soundstage, improved presentation. But my DR-6 was an older model that did not have balanced outs or a remote. I borrowed the LS-15 from a local dealer to try out. The tube pre was an even greater improvement. But I have to mention that the DR-6 and LS-15 are a decade apart. The CP-60 is Classe's current top of the line. If at all possible, audition some different pre-amps to see what works best in your system. Good luck!
