How many simultaneous dcc sends and initiated chats are you planning on? The only time I ever had more than 5 incoming ports running at one time is when a new release of mIRC comes out. (Then I could use about 50 ports and a much faster connection.) So 5000-5008 should be more than enough, and you don't have to forward the server (6600+) ports - to you they're outgoing, so the router doesn't affect them. Just make sure - again - that mIRC is using 5000-5008 for dcc. And make sure you're opening TCP ports, not UDP ports.
