Preferred Audio Output, USB or 3.5mm?

Miewan - Thanks for the reply. After more thought on this, I don't think the output (USB or 3.5mm) makes a difference since the output is through a DAC before the preamp. The DAC I will use (TC7510) does not support USB, so I'll use the 3.5mm output and no need for a USB DAC.

Jax2 - A TOSLINK TO MINI PLUG CABLE ( http://www.cablestogo.com/product.asp?cat_id=2001&sku=27015 ) allows connecting to a DAC from a 3.5mm. I use this type of connection with Airport Express and TC7510 DAC.

Ah, forgot about the mini-Toslink via the headphone port. I haven't actually tried that except for with an Airport Express and it was absolutely terrible. But that is a different device. In that case it will depend upon the implementation of the USB with the DAC you are using. If the DAC has poor USB implementation you might try using a DIP/dejitter interface which can go between either USB or Toslink, but would require an additional cable. I don't have any experience with you DAC to say whether any of this would be worth it. If it sounds good to you, that's really what's important.

HDMI would be the better way to go.

I do not think Mac's have HDMI ... at least not Mac Mini's (unless the latest models do)

No HDMI connectivity on an iMac