Which Digium card to choose?

Greetings! Currently we have 3 different phone numbers. The plan is to upgrade to Asterisk and use softphones ( Eyebeam ) to replace our old phones. We have 6 computers and we plan to have all these numbers connected to each of our computers. For example my computer’s softphone ( Eyebeam ) will have 3 numbers.

Question 1 : Is this setup possible?
Question 2 : Which card do i have to buy?
Question 3 : Besides the server, mic, and digium card what else do I have to purchase?

Thanks!

You haven’t said how your three numbers will be delivered. That is what decides what if any extra hardware is needed.