What is your budget?
What inputs do you need? E.g. USB, toslink, s/pdif
How many of each input?
What max sampling rates do you require? E.g. 24/96, 24/192, or higher
What type of digital? e.g. pcm and/or dsd
Some have headphone outlet - do you need that?
Are you a lazy bugger and need a remote :-)
Schiit has some excellent product starting from $100
I have the Schiit Bifrost with USB and UBER analogue upgrade - put a high quality power cable and interconnects on it and it performs extremely well. You could start with the base model @ $350 and then add the upgrades later.
The Gungnir is there TOTL - fully balanced design
All sound great, but none have a remote, so you have to get off your butt to select input type.
There are products from Teac, Wadia, Chord, PS Audio, m2tech, Cambridge Audio, Burson, Peachtree - to name but a few.
Decide on the features you need first - then we can make a better recommendation.
take a look at http://www.needledoctor.com/Online-Store/DAC to see a good selection and price range
One note of caution - some DACs do not process the same sample rate on all inputs - decide if that is an issue
Regards