You can do this if you are getting all your email sent in via an SMTP feed (costs more and is usually only available from a business class ISP). However that in the long run is more flexible if your business starts to expand, as exchange can then be used to handle distributution lists, etc in a far more versatile way.
The catch all POP account would have to be set up by your ISP, and then pointed at a specific POP mailbox on your server.
Usefull site for losts of SBS2003 stuff :
www.smallbizserver.net 