Cary DMS 700 vs Aurender A300

I believe you're referring to the Aurender A200 as it is comparable cost wise to the Cary DMS 700.  I can't speak of the Aurender as I've never heard it, but the Cary DMS 700 is a real sleeper.  I've owned it for over 2 years now and have no regrets or inclination to consider anything else in this price range.  Cary DMS 700 is made in USA and rarely comes up for sale on the used market and  Aurender is made in Korea if that matters.  Be aware that Cary can do Roon, Aurender is not Roon compatible to my knowledge.

My two cents: when I was in the market for a streamer/DAC, I gave the Cary DMS 700 serious consideration. (I even attended AXPONA that year to listen to it in an optimal setting.) One clear feature it had, in my estimation, was its being Roon ready. Ultimately, I decided on the Lumin T2, which has served me well. The Lumin unit has recently been upgraded to a T3, and I recommend you consider it as a possibility for you. While the Cary unit has much to admire, it is quite costly.

In reading the reviews of their products on the Cary website, I found interesting the comment regarding unbalanced vs. balanced outputs. The sense I got is that its noteworth performance is somewhat dependent on using the balanced outputs. Consequently, don't lay out that amount of money unless your preamp has balanced analog inputs.

I had a Aurender A100, Cary 600,700 and a Lumin T2 so maybe I can help. 
The Aurender and the Cary both use AKM chips. While the T2 uses the Sabre chips

You can’t beat the Cary for features. Wireless,Bluetooth, can be used just as a streamer, SD card playback etc. Swiss Army knife. Will always sound good, never fatiguing . Their app is good but quirky.  For me it just didn’t dig deep. I moved on to  a Bricasti which just sounds much bigger and lively. 
The Lumin T2 sounded great on 90 percent of the music played on my system but with the Persona 5F beryllium midrange and tweeter could get edgy, ,but if the rest of your system is on the warmer side of neutral it may work well. 
 

Have not heard the A200 but I assume it will be similar to the 700 but have the advantage of local storage which the Cary lacks. 
 

Really comes down to features as they are both great companies

 The Cary’s remote is the best I ever used as it will run everything if you lose Wi fi. The Cary’s manual is 80 pages and written very well. 

I don't know what Aurender's policy is, but Cary allows a 30 day trial period, you just pay return shipping cost.  Another difference is Cary sells direct to consumer which may be a better value and if you're buying new, Cary Direct runs sales throughout the year if you're patient.

Great financing also on the Cary