I am using a T1 with a pair of Grado SR80's and it's a nice little setup. the DAC section is what encorporates the tube from what I have read about it.I had mine shipped with a 6922EH instead of the standard 6n11.
The build quality is excellent , switches are solid ,fit and finish is great,and the volume pot is very smooth.At $149 ,it's a great deal if the shipping isn't too expensive.I bought mine in Canada through Springwater audio, great place,just below the $200 mark with the tube upgrade.
Maybe not the lowest price a trusted retailer with good service.
It also has 3 gain control settings ; 0db,+10db and +16 db. USB is plug and play through my laptop with windows 8.
Soundwise ,It's a big step up from just using my onboard soundcard and although my Grado's don't necessarily need an amp ,they do benefit from it in a big way.I have no other experience with external DAC/AMPS so I can't really give you a comparison.
I'm a huge tube fanboy from my guitar background ,which drew me to this like a bear to honey. The exposed tube with the underlit led(indicates the unit is on and ready for use as there is a 30 second warmup period when first turned on) is a conversation magnet(cool factor) I don't think you can go wrong with theT1,there is another forum I think in the UK that has more discussion on this.
If you get one,post back here and tell me what you think. Glenn