I have a Nationite s-flo which is a rebranded Teclast T50, somewhat of a predecessor of the T51. It has a smaller screen, single DAC, FM and 8GB storage. There is no line-out nor external card support (the T51 does have both, I think). It does't have playlist support either. The sound quality is quite good, and it has pretty good eq functions. However one thing that plagues all the chinese daps that I have come across (i.e. onda, teclast, ramos, jxd etc) is that the screen when turned on produces a small clicking sound through the headphones. It does go away when the screen is turn off, and sometimes it's not very noticable, but it is there when the screen is on. The other thing with the T50 is that the touch screen is very sensitive, which is good, but it can also go nuts occasionally in low temprature an what not, so the hold button is my best friend when I use it. But even with all of its shortcommings, I still use it all the time, and I'll be keeping an eye on the T51 as well.