Soundcards with wordclock input

I've read that if you use a common wordclock between transport and DAC, then you can reduce (eliminate?) jitter. I've seen only one card that has a wordclock input made by Marian. Are there others or others that are better?

Also, is it better to use 1) a soundcard with a wordclock input or 2) a USB device (e.g., Waveterminal)? It seens that you would need a wordclock input in the Waveterminal to eliminate jitter between the Waveterminal and a DAC.
i've got the same hopes as you and am trying to run my DCS elgar+ into a MAC/PC. I've found a few high-end PCI cards with a wordclock input and AES/EBU balanced outputs, but i'm still trying to determine the best way to run the elgar in master clock mode and have the PC accept it. Here's a link to where i've found the cards and the people are as helpful as they can be:
trying to find out what the highest possible resolution is from MAC/PC given this setup, i.e 24/192?
It seems like we're in the same boat, since I'm considering the Elgar+ (or the DAC6e). Currently, I'm leaning toward a device that converts USB to digital (e.g., s/pdif, AES/EBU, or I2S). There's no jitter with USB. I'm pretty sure that USB won't do 24/192, though -- I'll let the Purcell or DAC6e upconvert 44.1. But it seems like the UBS-to-ditgital box could still benefit from a wordclock to eliminate jitter between it and the DAC -- I haven't seen one with a wordclock. Empiral Audio and Hagerman make USB converters.
a few of the RME professional cards on the link i sent you have a BNC WC input and appear to output 24/192 via AES/EBU, which, i imagine is quite a bit better than a converted USB to AES/EBU and provides the wordclock solution we're looking for? i'm still a bit confused on how to get the quality of source file we need to get the card to put true 24/192 into the card to make this all worth the trouble?
Look at the soundcards made for studio recording professionals, like the above-mentioned RME. They often have word clock ability. But even within this group one must be careful since judging by specs alone is worthless. I run a pro recording studio, and can tell you that two different pro audio cards, similarly priced with the same specs can sound completely different. One can be sweet, open, and three dimensional, while another with the same specs can be rather brittle and closed sounding. It mostly has to do with the quality of the converters. RME is an amazing choice, as are products made by Lynx, and Apogee. I would not recommend Mark of the Unicorn, and Emu has a great bang-for-the-buck card - the 1820M - that rivals the 1st three mentioned.
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.
Wordclocks do not eliminate jitter. They may improve it, but the effective solution is a clock inside the DAC, not external.

Steve N.
Empirical Audio