To make it simple:
- for good line and short, enough will be old Huawei modem
- for long or bad line zyxel (VMG1312-B10A, as example, also good for any line)
If cabinet turn out to be eci, in spare time could be tested something with lantiq chipset.
Recommended choice on this forum (one of, zyxel VMG1312-B10A) is probably the best for start, no matter on what cabinet you are, I got one to mantain my line when dlm got a bad week and for that matter is probably one of the best, even that on daily basis I use modem with lantiq.