Here's the takeaway from my previous post...
If possible, you need to hear the amps under consideration in your system to make a good decision.
Having owned the Leben CS600, I can verify that it's a fine product with exceptional build quality that should drive the Living voice IBX R2 speakers without any problem. Mine was dead quiet. In fact, it was the quietest tube amplifier (integrated or otherwise) that I have ever had in my system. However, I cannot offer an opinion as to how the combination will sound.