@gizz72
Yes I have one of the cables installed to my modem. (correct me if i'm wrong) a DIN25 to DIN9(this one would definitely need a 'Gender Bender'). and The other cable I bought is both DIN25 to DIN25.
You need a "null modem." It usually looks like a standard gender changer, but it's not. This device inverts the send/recieve in a serial connection.
The standard modem cable is a straight through. Plugging it directly into another Amiga won't work. Picture it like this. The serial port has one pin for sending data, and one pin for recieving it. If you connect two computers directly together, when the first machine sends data, it's going to travel straight to SEND pin on the other machine, instead of the RECIEVE pin.
In other words, the TX from one Amiga needs to be connected to the RX on the other, and vice-versa. A null-modem fixes this for you, and allows a connection. :-)
But with the null modem and a standard serial cable (and possibly a gender bender, if needed) the connection is as safe to the Amigas as using a regular modem. :-)