[Darryl Ramm]

You can use whatever DigiLink IO boxes you want 96 IO, 192 IO, HD IO, Omni, ... with the combination of analog or digital cards in them you want that meet your analog or digital connectivity needs. Omni can do basic monitor control and has two build in preamps/DI and and is a convenient box but you don't *need* an Omni.

An Apollo 8 quad? Apollo Twin Quad? The bigger Apollo Quads have ADAT/SMUX Out and you can go into ADAT/SMUX In on digital IO cards on any of the DigiLink interface boxes. The documentation for all those IO boxes is very well written and all available on the web. HD IO uses different IO expansion cards than the 192 IO and 96 IO,

Nobody here can guess what your other connectivity needs are, what you are trying to achieve, or your budget, so really cannot help you with any more useful advice.

Working with TDM DSP plugins vs. UAD DSP plugins is a different world. I wonder how long UAD will support RTAS UAD plugins (which you are trapped on forever with TDM Hardware and Pro Tools 10). Hopefully none of that is a surprise for you and you have a reason for wanting TDM hardware. And hopefully you purchased a PCIe card set.