Router query - DG834G firewall rules

I have a netgear DG834G that I'm more than happy with, but I'm about to move
to cable from ADSL, so I thought I'd order the WGR614 which was (I assumed)
pretty much the same router minus the ADSL modem.

However, it looks like it only has a restricted version of the port
forwarding/firewall rules functionality that the 834 has, ie, I can set up a
rule:
forward incoming port 80 to local IP blah
but I can't filter it by external IP, ie:
but only allow IPs in the range X to connect

Have I missed something? And if not, any suggestions for a
wireless/cable/router that will allow this?

Thanks