You can buy a brand new Musical Paradise MP-D2 Mk III and have a good bit of cash left over.
I actually own the NT-505 and the MP-D2 though the first version with the AKM 4490 chipset. As a DAC only the sound is similar though the sound of the MP-D2 can be "tuned" quite a bit with the various input and rectifier tube combinations. So if DAC only is what you need then the MP-D2 is a good place to start. If you need or want the streamer and don't have another DAC then the NT-505 does a lot of things right.
I have the first version of the MP-D2 with the AKM 4490 chipset. I don’t suspect the difference between the 4490 and 4497 is that great and I would never order one with the ESS chipset as that is not what the DAC itself was designed around. The major updates to the Mk III are in other areas like the power supply and the USB modules. As to the NT-505 the only two main dealers are Sound Approach and HiFi Heaven and the price is the same though as they are distributed by Onkyo in the US any Onkyo dealer should be able to special order one. Even at it’s $1999 selling price it is still $300 less than the Lumin D2. It’s kind of a pick em as to the DAC so it comes down to if you want the streamer or not.