Isn't it better to OPEN the ports to your WAN address than to forward them to the LAN?
see my other post in iptables topic, but generally
iptables -I INPUT 7 -p tcp --dport 2700:2710 -j ACCEPT
should do the job for 2700-2710 work
Anyway, due to masquerade is could work also with FW on and no port open
BTW: enhanced-ctorrent uses 2706-2106 as default
Unofrtunately, I am almost unable to get any download to reasonable speed (5-10 times slower than utorrent behing the router) - even disabling the firewall does not work :-(