We have the Cambridge 840c, which I think has the same input options as the 740c. I have often used this both as CD player and also fed it from my MacBook (and also my Airport Express and MacMini) via the optical Toslink, without any problem.
You need to switch between sources on the Cambridge, but otherwise don't have to move any cables.
You do need the special optical cable connecting from the 1/8" combined audio out port on the Mac to the standard Toslink input on the Cambridge.
I didn't pay much attention to the difference in sonic qualities between CD and the computer sources due to the reportedly higher jitter associated with the optical connection, but didn't find that route much inferior and certainly worth listening to, given the convenience.
And you can later always upgrade that path by switching over to the USB->SPDIF route: we now use the M2Tech HiFace, going from the Mac via USB and the HiFace into the SPDIF port, mostly to allow higher sample rates than Toslink supports on the Mac.
You need to switch between sources on the Cambridge, but otherwise don't have to move any cables.
You do need the special optical cable connecting from the 1/8" combined audio out port on the Mac to the standard Toslink input on the Cambridge.
I didn't pay much attention to the difference in sonic qualities between CD and the computer sources due to the reportedly higher jitter associated with the optical connection, but didn't find that route much inferior and certainly worth listening to, given the convenience.
And you can later always upgrade that path by switching over to the USB->SPDIF route: we now use the M2Tech HiFace, going from the Mac via USB and the HiFace into the SPDIF port, mostly to allow higher sample rates than Toslink supports on the Mac.