Need to get a Digium card but confused on which one.
Small school in Australia
-Upto 3 PSTN Lines on a Line Hunt (One is Busy it goes to next line)
-4 IP Phones in the Classrooms.
-4 Lines to a EnGenius Phone System (Longe Range) 4 PSTN lines on the base station.
This is as big as it will need to be, more phones will all be IP in the future.
Thanks 
You need 3 FXO ports (for the inbound lines) and 4 FXS ports (for the EnGenius phones).
I would suggest you get a Digium TDM800P series as that will give you 8 ports (you need at least 7). At a minimum you would want a TDM843P, but if you can afford it I would just get an TDM844P as that will give you an extra FXO port if you decide you want a fourth incoming line.
Howdy,
swaterhouse is correct.
Go for the TDM844 though as the TDM800 platform doesn’t support port configurations numbering seven - TDM843 isn’t possible.
TDM844B for sofware echo cancellation; TDM844E for hardware echo cancellation.
Cheers.