I think the separate external clock/DAC/transport is an old way of solving the problem for hifi. A clock is fine in some complex recording studio situations where multiple digital systems needed to be in sync.
But I would suggest you save your money and spend it another way. The advantages like better dynamics, clearer soundstage and focus can be had for cheaper.
Just buy a computer based set up with a new top of the line firewire DAC. You will be shocked at the sound quality. All those old problems of sync will be solved in 2 purchases and for a great deal less than a brilliant but redundant external clock.
If all you are doing is playing CDs move into the 21st century. Play from cache with nice software. The sound is sublime. Playing redbook in real time will not compete. That old 1990s way of solving the problem is over and is too expensive. Been there and done it with DCS. You will never look back. You do not need to be that computer friendly. A mac of some sort will be easiest computer to set up and make sound good. Once it is set up it is done.
If you have a large selection of SACDs it is a bit of a pain, but you could still transfer SACDs to HD. Besides once you get into 24/192 downloads you will probably forget about SACDs.