Fairly new to streaming. Where to start?

Yes, you can use another DAC with the Node 2i. You should also take the app interface into consideration. This is an area where Bluesound excels.

If you already have a bunch of digital music and a way to continue ripping CD's, then the Vault would be redundant.  All you really need is the Node 2i.  As long as your music is available on a shared drive on your network, the Node 2i can access it.

@artemus_5 I'm not familiar with the Yamaha unit you mentioned.  How's the interface?  One of the Bluesound's best features is its app.  Keep that in mind when making your decision.

As to your question about "better 1's and 0's", I've yet to see a definitive answer about that.  What I can tell you is that I went from a Bluesound Node 2 paired with an Auralic Vega DAC (which was $3500 when new) to a TEAC NT-505 streamer/DAC and it sounds better than the Node 2 / Vega combo did. 

I also tried my Node 2 with a Mytek Liberty DAC and the DAC in my Sony TA-ZH1ES headphone amp (which is very good).  They all improved the sound of the Node 2, but none of them sounded as good as the TEAC all-in-one device.

My thinking is that the streamer does matter, as it seems everything matters in the signal chain, but no way I can prove that.  I have no way of testing the streamer in the NT-505 with an external DAC.

My music files are on a 7200 RPM spinning drive in an external enclosure that I share on my network.  I have not had any issues with lag or anything else when streaming to my Node 2.  And I'm sending files over my wireless network, the connection is not hard-wired.  

I don't doubt that having it hard wired and connected directly to the streamer might have some benefit, but the DAC is probably the weakest link in the chain if you're going with a Bluesound product, not the hard drive.

@artemus_5 Perhaps I didn't make my point clear... if you want to get the best sound quality, consider something other than the Bluesound line.  Investing in something with a better DAC will have more of an impact on sound quality than whether the files are stored on a spinning hard drive or a SSD.  Most of my digital listening is through streaming services like Qobuz and Tidal, where files are quite possibly not even on the same continent and unlikely to be stored on SSD in their server farms.  Sound quality is excellent, and more so since I replaced my Bluesound with a better streamer (the TEAC NT-505). 

In other words, it's unlikely to make much difference if the Vault has a spinning hard drive or an SSD.   I doubt it's a SSD, or they wouldn't say "ultra-quiet" 2TB hard-drive.

The TEAC NT-505 is both a streamer and DAC and was a noticeable improvement over my Bluesound Node 2.  It also allows me to stream files from my network.  I paid less than $2K.  The Lumin D2 is the other one I'd look at around your budget.  Retail is $2300 for the Lumin.

I second the Bluesound approach - excellent app then you can upgrade the DAC. Lumin D2 has a far less friendly app, does not have an antenna, and support from Lumin at least in the USA is non-existent. The access to all the streaming radio stations in the world will be a revelation. Tidal on the internal Bluesound DAC is pretty darn satisfying for all but those who sit in the perfect listening position imitating Jonsey from the Hunt for Red October.

Let me start by saying I don't own a Lumin, so that I'm not perceived as a "fanboy".  My TEAC NT-505 can use the Lumin app.  I agree that the Lumin app is not that great.  The Bluesound app is really good and one of the most compelling reasons to go with Bluesound. 

I am using BubbleUpNP instead, which cost all of 5 bucks to get the ad free version.  The one thing that BubbleUpNP won't do that the Lumin app will (as far as I know) is stream internet radio stations, including Radio Paradise (which is the best of them IMHO).  You can always switch back to the Lumin app to listen to internet radio.  I have both on my phone and tablet.

The difference you'll hear between a really good DAC and the very decent DAC in the Bluesound has more to do with the quality of your other components than your listening position.  The difference between the sound of my TEAC and the Bluesound was more than subtle.

Some have suggested that I spend $200-300 +/- for a player/dac. Do you really think that will sound good or be competitive in my system? Of course not.

The Node 2 was a good way for me to dip my toes into the world of streaming, but the turning point for me was when I spent some time listening to the same song on my two turntables, my CD player, and the Bluesound. 

Obviously there are a number of factors that contribute to the sound quality, the recording itself, phono stages, cables, etc.  Having said that, the Bluesound was the least good sounding source in my system.  And I was using my Auralic Vega as the DAC instead of the Bluesound's DAC.  I never thought the Bluesound sounded bad, but it wasn't as good. 

After upgrading to the TEAC NT-505 I've had thoughts of going all digital.  I enjoy spinning records too much and they do have their "magic", but the playing field has been leveled, if not tipped in favor of digital due to the convenience factor and access to an exponentially larger collection of music than I have at my fingertips through streaming services.  I know you've said you don't plan to use any streaming services, but you should really give them a try.  Sound quality is excellent and it greatly expands your music library.  For the price of a few lattes, you can have an enormous library of music available.

Starting out with something like the Bluesound might not be in line with the quality of the rest of your system, but it will give you a chance to find out if streaming is for you or not.  I bought mine as a demo unit and flipped it for about what I paid for it when I upgraded.  The Lumin D2 or the TEAC NT-505 would be in line with the rest of your system and both are around your budget.  If you're convinced that streaming is something you'll use and enjoy, then I'd just skip the lower end stuff and start there.

I meant to mention earlier that if you want to stream over wireless and are looking at a device that doesn't have wireless capability, it's really easy and inexpensive to set up a wireless access point.  It's like a wireless receiver that you can connect an ethernet cable to.  Here's the device I use. 

https://www.newegg.com/tp-link-tl-wa801nd/p/N82E16833704052 

I have it connected to an ethernet switch that my streamer, roku, TV, Oppo bluray player, and home theater processor are all connected to.  Works great!

Many recommend a direct wired connection, but that's not practical for everyone.

Would Node 2i improve the output digital signal compared to that of OPPO?

The 105 has a pretty decent DAC.  Probably not.  You might get better sound quality sending the signal from the 105 to an outboard DAC.