What hardware is needed?

I downloaded Asterisk now. I have a PC with Linux installed and would like to build a developement system out of this for possibly changing over from our old ROLM PBX to an open platform like Asterisk.

What do I need for hardware. A digium board? Since this is a proving concept, all I will need is a single T1 Digium card.

Do I have this all correct? Or is there something else I am missing?