On a 1-5 star rating:

5 stars for the DAC/Preamp (considering its price point)
4 stars for the Controller App. (works well with a few annoyances)
3 stars for the documentation.
2 stars for no WiFi.
1 star for its native file handling capability BUT with a freeware software solution it becomes 5 stars (see below).

This review is more focused on providing a review of the functionality of the DAC of those things that may not be obvious from the documentation. To keep this as brief as possible I am intentionally not restating what can be found in the product documentation since you can read this for yourself.

While I am calling this a review, I am purposely not saying much regarding sound quality which is so subjective and system / room dependent. But I will say I am very happy with the sound quality of this DAC. I upgraded from a Bluesound Node 2 and realized significant and noticeable improvement in sound quality plus higher resolution and DSD.

The controller app itself is pretty good but a lot of its functionality is not documented so you also have to figure it out on your own. Once you do you will realize it’s pretty good. It just takes some time to get used to. There are a few functional annoyances but that may just be because I am used to using the BluOS app.

STREAMING SERVICES work very well. I tried it with both Tidal HiFi and QoBuz HiRez. The MQA decoding of Tidal sounded excellent, so good I am not renewing my QoBuz.

REQUIRES A HARD WIRED ETHERNET CONNECTION because the controller app will not work unless the DAC is directly connected to your router via Ethernet. You should not purchase the NT-505 unless you have a hard wired Ethernet connection available. The DAC does have both coax and Toslink inputs so one could use an external streamer connected to the digital input on the DAC but then you would have to use the streamer’s controller app and none of the other functions of the NT-505. That really wouldn’t make sense.

MUSIC FILES ON A SERVER OR NAS: The native file handling capabilities of the NT-505 are awful if you have a large number of music files. It is slow to load and every time you turn on the DAC or your controller app it seems to take forever to re-load. I was ready to return this DAC until I noticed a single line in the documentations were TEAC recommends third party free ware called MinimServer to access and manage music files instead of their own software. You MUST use MinimServer if you have any significant amount of music files in your library.   MinimServer is very fast to load large amount of music files and more importantly maintains the index of music files in the server’s memory even when the DAC is off so it doesn’t have to rebuild the index every time you turn on the DAC. MinimServer performs very well with 1T of music files that I have stored on a remote PC. If you have a NAS compatible with MinimServer you can install MinimServer on the NAS and then use another free software called MinimWatch on your PC to configure and control MinimServer. MinimServer and MinimWatch are both very well documented and a Google search will get you all you need to know.

MUSIC FILES ON LOCAL USB DRIVE: The local USB port on the front of the DAC is intended for USB thumb drives but with this configuration you can’t use MinimServer and are limited to using the DAC’s native file management with the limitation described above. But with a smaller number of files this isn’t that much of an issue. I tested it with a connected HD with about 200 GB of music files and it did ok but when I tried loading more the DAC choked and froze.

PLAYING MUSIC FROM A COMPUTER: There is a USB type A-B connection on the rear to connect a computer directly to the DAC but I have not tested it since this DAC can play all high rez and DSD files from the a remote server or NAS.

I am not going to plug any source for purchases except to say that I bought the DAC from a large online seller that offers a 60 day return for any reason with full refund or credit for something else. That is more than enough time to fully evaluate this DAC.

83b78019 99ac 4fa2 94b1 64a12b0168361extreme
I did it for a while with a TP Link WiFi extender and now with a cable from an Xfinity Pod.  Never had an issue with either.  
It might work. It might not. I used a TP-Link WAP. Don't know why it didn't work. Everything else did. Could have been something with my network. Who knows?
Clarify. Are you trying to upgrade to a better DAC? If you are happy with the DAC in the C2500 you don’t need the NT-505 you just need a WIFI streaming device to connect to the digital input on your C2500. Plenty of WIFI streamers to select from.
I am a fan boy of the Node 2’s. They work great with WIFI and I personally like the BlueOS app that controls all Blue Sound products. Have two "higher end" systems with a Node 2 in each connected to external DACs. Love the sound. You can buy a pre-owned Node 2 for a couple of hundred bucks. I have yet to find a good justification to upgrade from the Node 2 to the Node 2i.
I use my nt-505 with an Ethernet connection now, but in a few years when I hope to upgrade to Bartok in my main system, I’ll move the nt-505 to my secondary system and use a Netgear wifi extender there, and run an Ethernet cable from the extender to the nt-505.

Currently in secondary system have Cambridge Azur 851n streamer/dac and separately Bluesound Powernode 2 (use them separately, mostly Azur, sometimes Bluesound), both wirelessly connected to the netgear wifi extender. Get dropouts rarely (once in 10 hrs?) on that secondary system. Absolutely never get dropouts in main system with Teac connected (Supra cat 8 1m Ethernet cable) by Ethernet to Netgear cable modem.

The nt-505 destroys each of the other two streamer/dacs in performance. Not close.
Someone in this thread did mention Teac CG-10M, anyone has experience using this master clock? Need some opinion from you.

I did buy a cheap master clock ($300) hook up my Teac Nt-505, the result is not so obvious, almost undetectable if not doing A/B comparison.