Just joined the forum as was researching an all in one DAC-AMP setup that won't break the bank. I was laser focused on this DX3Pro+ model. The feedback of issues with the volume knob and also some crackling noise has me step back a little. Also the annoyance of the smaller headphone 3.5mm input. So I kept on searching for other 'newer' models around $200 and found that Fiio has released a similar 'chipset' all in one unit called Fiio K5 Pro ESS. It does not have bluetooth but that is something I do not require when the setup will be plugged directly to my desktop. Also I don't care for a remote or display. The main advantages that matters to me with the Fiio ESS is that it has a larger 6.35mm jack and 3 levels of gains. The advertised 'audio measurements' seems a bit more conservative than what Topping has listed. One big disadvantage of the Fiio I can see is that it has had a $50 price increase over the previous K5 Pro and now is $200 USD. More info here: https://www.fiio.com/k5proESS
P.S. I am no Fiio shill, genuine enquiry, what do people here in the know think of it compared to the DX3 Pro+?
Currently testing the DX3 Pro+ against the Loxjie D30 which I got around 260 euros in Europe. This might be in your budget.
Indeed the Topping build quality is much cheaper. The Loxjie feels more "premium" and better finished with a better screen and menu system, integrated power supply. The volume button is super smooth. I've been trying to spot the differences in terms of sound quality, but it seems that for my usage with Hifiman Sundara, they both sound very good so far. The DX3 volume knob is indeed a little cheap and plastic sounding.
On the other hand the topping is easier to use for basic features without the remote. I often switch between line out and headphones amp mode and it is just a double clic away on the DX3. It also eats up less desk space while having a more readable screen. The the small jack is not as bad as all my headphones and IEMs have a small connector.