I'm using Tara Decade digital cables with my Theta front end and I'm quite happy with the sound. The Apogee digital cable is also excellent and usually sells for about $35 on the used market. Highly regarded by most people.
digital cable for theta front end
Using Theta Carmen (first version) and Pro Basic IIIa DAC. Currently using a Tara Labs digital cable, but hear not much improvement over a basic monster cable digital cable. Rest of system: Adcom GFP750 preamp, Bryston 4B-NRB amp, Snell CV speakers (with Rel Storm-III sub). Synergistic Research Kaleidoscope Phase II interconnects, Tara Labs Air 2 speaker cable. Anyone out there with Theta front end (or otherwise) have digital cable suggestions? Thanks. -Dave