The first time I had come across a highly precise (and expensive) femto clock in a DAC was at last year's CES in the MSB room. This year Calyx says they have added a femto clock into their new DAC which is available now and retails for $6850. Inputs include two coax, two optical and two AES-EBU in addition to a BNC and USB jack. All inputs handle up to 24/192 and there are both balanced and unbalanced outputs.