I use to own the Leben CS600 which had more than enough power for my Living Voice OBX-RW speakers. I agree the CS600 is very well made with no operational issues and the sound quality is excellent - well extended, slightly warm and rounded but not classic sloppy vintage tube sound.
As you may know you can tailor the CS600 sound by easily substituting different output tubes.
However the CS600/Living Voice combo wasn't totally satisfying for my taste. Although the CS600 is dynamic and full bodied, I preferred the more incisive and upbeat sound of the Patek gainclone (40w) and the Leben CS300 (12w). These amps complemented the neutural tonal balance and excellent pace, rhythm and timing nature of the LV speakers.
If possible you should audition the CS600 and CS300 with your IBX-R2.
As you may know you can tailor the CS600 sound by easily substituting different output tubes.
However the CS600/Living Voice combo wasn't totally satisfying for my taste. Although the CS600 is dynamic and full bodied, I preferred the more incisive and upbeat sound of the Patek gainclone (40w) and the Leben CS300 (12w). These amps complemented the neutural tonal balance and excellent pace, rhythm and timing nature of the LV speakers.
If possible you should audition the CS600 and CS300 with your IBX-R2.