Hardware advice

I’m new to asterisk and I want to start experimenting with it. I’d like some advice on what hardware to use to connect ISDN lines to the server. I guess I’ll use one of the fully supported cards from asterisk.org/hardware

The information about the cards there is a bit vague to me, perhaps that’s just because any card would do for me. However, I want to make sure of that. I plan to attach a 8-line ISDN connect to the asterisk server, what card should I use? (Furthermore, what exactly is the difference between having a quad-span, a dual-span and a single-span card?)