There's a DAC where I've enjoyed the sound of very much with my Grado RS1i, PS-500 and Magnum X headphones. Though, it is hard for me to give a full recommendation at the time due to a few items of concern. The DAC is the Fiio E10.
Concerns:
1) Noise. When you pause your playback source (e.g. - Foobar) you can hear a light "ssssss" sound that I wish it didn't exhibit. I've tried many USB cables to see if this could be resolved. I even purchased a new Thermaltake power supply for my computer and thought the sound issue might be resolved. * Though, it really wasn't. I've even ran my computer with an adapter to lift the ground in the event the noise was created by a ground loop. Again, not much luck.
2) The 3.5mm female connectors. These connectors exist on both the headphone out section where you can use the headphones without a separate power amp; and, the second 3.5mm output, which is a line out and permits you to use the E10 strictly as a DAC to run to your power amp.
To me, these issues are a bit saddening. The DAC itself, though, was capable of providing some excellent sound with the Grado signature headphones. Clean percussion, clean strings, etc. I was quite amazed by such performance in a DAC at that price level. Really.
So, the question that comes to mind is, why did I post this response if it wasn't a solid recommendation? Well, I wanted to share how good it can sound - due to great potential. But, I felt that the noise issue when no music is playing was a concern of mine, as well as the very cheap 3.5mm female jacks. If those two issues could be remedied, I feel this would be a super steal at $65.00 or so.
As to other DACs - e.g. - Modi, oDAC, etc., I would ensure that you have the capability to potentially hear them first before making a leap. I've read about some people making comments on the sound signature. In fact, on member, TMRaven did a review on the O2 amp / oDAC combo and the Schiit Modi / Magni combo. His review was short and sweet. He said to buy the Modi / Magni combination. I've had the Modi / Magni stack before and held onto it for a few weeks but sold them off since the sound was a bit "thin" to me. Again, just my view, but I've been in this game a long time and tend to try and be as objective as I can.
I think all too often, people will recommend items that they currently own. But, it should all come down to what our ears and what we can appreciate. Just for me to tell you that product "x" is very good, doesn't mean it's 100% right for you, or what you may want to hear from your music system.
Research carefully. Buy carefully. Enjoy and Good Luck!