I own the Theta Miles (unbalanced) and am very pleased with it. As to your concerns about the analog volume control being old technology; I don't think old necessarily makes it bad. The analog volume control is supposed to be better than digital and is used by other higher $ cdp manufacturers. I'm not sure that you will find the balanced Miles at $1k (usually $1100-1300) but who knows.
I haven't heard the Arcam so I cannot compare them to the Miles. I can say that the Miles is forgiving of poor recordings, has a good soundstage, plays all things well, and has great bass extension.
I haven't heard the Arcam so I cannot compare them to the Miles. I can say that the Miles is forgiving of poor recordings, has a good soundstage, plays all things well, and has great bass extension.