As I understand it, Amvona is out of business - I think Henry's bought all their remaining stock when they closed.
I have an Amvona tripod and pistol grip head combination that has functioned well for years with my medium format cameras, but as I understand it their quality control was somewhat inconsistent.
I would agree with CGW about the number of sections in a monopod with one qualification. If you are intending to use a monopod when travelling, or want one that will store unobtrusively, the 3 or 4 section models collapse to a smaller overall length.