switching from analogue to isdn

I am currently running an asterisk server (using kubuntu linux) with one analogue fxo port. We would like to upgrade to 2 lines so I can forward incoming pstn calls to cell phones. I see that asterisk doesn't natively support ISDN and therefore you have to load thirdparty drivers. Have people got this working easily or is it a big mission? I have seen that people have got duxbury isdn cards working and therefore would also like to know if using these cards reduces the echo that i experience with analogue? Also does asterisk easily pickup call termination from the pstn party? (i had to set my asterisk to listen for hangup beeps which is not a very eligant solution)

I'm using the duxbury isdn card with AAH (CentOS), currently upgraded to Asterisk 1.2.3, system works fine, no echo problem, and PSTN hang up properly.

use this script to install, pretty easy, pls refer to my old post at

http://mybroadband.co.za/vb/showthread.php?p=418620#post418620

I didn't use spandsp for fax send/receive, it works fine, but too slow (9600 only), according to the developer, they are not going to do 14400 because the license issue (no open license). I install the HylaFax instead, with an old fax modem, work perfect (hylafax is a very stable open source fax server, i had another installation running for 3 years already, handle heavy fax task, easy to set and use, no maintanence needed at all