Now that I think of it, I kinda want to use it for my laptop or ipad at work... Does the odac work on iOS devices? I'm kinda leaning towards the C5D because I don't need to plug the amp to a wall socket, But if the quality of the dac / amp of o2+odac combo is cleaner and better than the C5D, I will go for the o2+odac and just make it my desktop gear at home.
The O2 amp overall is better but C5D is not far behind. This is actually what I use most of the time. I have not tried the ODAC. I suppose you are better off with C5D since it's more versatile. Given the C5D's size SQ quality is not night and day.