Theoretically, and DAC with jitter correction circuitry on board will do an excellent job of eliminating the need for an external word clock. My last two DAC's were the Musical Fidelity A3.24 and Audio Research DAC-5, both with jitter correction circuits.
I'm now upgrading to a Wavelength Cosecant (with zero jitter as spdif is eliminated from the chain) and can tell you that the dynamics and timing of the Cosecant is about the same as the other two outboard boxes. The Cosecant is head and shoulders above them in other sound quality attributes, which is why I'm moving in that direction (note: the Brick is no slouch either)
Anyway, short version: you don't need an external word clock, so save your money on the audio interface and put it into a better sounding DAC. If you're already at dCS level and are trying to tweak to the absolute peak of perfection, why not just try some of the options as you're probably aiming for small changes that the rest of us wouldn't be able to hear in our systems.
I'm now upgrading to a Wavelength Cosecant (with zero jitter as spdif is eliminated from the chain) and can tell you that the dynamics and timing of the Cosecant is about the same as the other two outboard boxes. The Cosecant is head and shoulders above them in other sound quality attributes, which is why I'm moving in that direction (note: the Brick is no slouch either)
Anyway, short version: you don't need an external word clock, so save your money on the audio interface and put it into a better sounding DAC. If you're already at dCS level and are trying to tweak to the absolute peak of perfection, why not just try some of the options as you're probably aiming for small changes that the rest of us wouldn't be able to hear in our systems.