Have both the Topping E30 and the E50. The E30 was just OK, nothing special. The E50 was on a whole other level. Like others have noticed, the bass was tighter and more impactful. Very smooth sounding DAC but with plenty of detail. But the number of new DACs coming onto the market is mind boggling. Hard to even keep up anymore!
My current favorite DAC is the iFi ZEN Signature V2. Compared to the E50, it seems to not be quite as smooth but has even more detail and a huge soundstage. However, I'm using it on Tidal Master Edition with MQA and it is a full rendering MAQ DAC so I'm sure that is also part of the sound profile difference. The Topping E50 also does full MQA put just doesn't sound as detailed as the ZEN Signature DAC to my ears. Frankly, I'm surprised that DACs sound so different as I had been told that DACs all pretty much sound the same unless you go way up the price scale. Not my experience.