I had the Topping TP20 hooked up when the Sure amp arrived, and at the time I was convinced the Sure sounded better. I pulled the Topping out of retirement today, and now I'm not so sure. The first thing that is noticeable with the Topping compared to the Sure is the increased power. While I routinely crank the Sure past the 50% mark when I want to get some real volume, the TP20 has plenty of output and puts out more volume than I'd ever want with my system well before the half way mark. It's also much stronger in the bass, maybe a bit too much for my taste.
The Topping TP20 looks more expensive, and it is. It's got a front mounted volume control and a pleasing blue ring around the volume control to indicate it's on. The Topping is hard to fault. My recollection is that the Topping has more output and sounds better than my Hlly Tamp-20, which is another TA2020 model. I'll have to pull out the Hlly and do some A/B comparisons. At this point though, I'd have to say the Topping TP20 is an easy thumbs up, and it is my current favorite TA2020 based amp, and it's giving the Sure a run for the money as my all time favorite T-amp.