It depends on which tracker you download and how fast your Internet Connection is.
For example, when I download from public trackers my dl speed is crappy because people are shit and cap their upload because they don't care anymore as soon as they get what they want.
On a private Tracker where you have to keep your ratio you don't have this problem and normally can download with full speed, which in my case is 10Mb/ sec.

And a Seedbox is just a box which has a good Internet connection,...