My buddy uses an older Cary 301 as a transport with his 21 DAC linked with a Kimber digital RCA cable. Both tube units seem to match up pretty well. He bought all his stuff from John at Audioconnection and seems very happy with it. I wouldn't go specifically looking for a 301 however, as it is a bit dated and may be hard to find anyway. We also tried My Wadia 23 as a transport on his 21 and that too did great. I think the Theta is a very well designed product. A Data Basic II or III would be a good unit. Many guys seem to like the Modded Sony 770 as a transport. I think also a used CAl delta would be a good choice.
Best, Ken :)
Best, Ken :)