how do i get 3 360s to have open nat on my netgear???

[sway]

as it says peeps,i got a Netgear DG834G V3 and it works fine for my pc and the misses laptop but me and my 2 boys got an xbox 360 each,but how can i get us all to have an open nat,if im on open they will be on strict or moderate,i have turned off the firewall and all ports are open on the router,but with my linksys router we are all fine,but its a bit dodgy and the wireless part disconnects a few times a day and is annoying because we are all wireless with the 360s,i would prefer to use the netgear as its better i think.
i have tried everything set the 360s to automatic and also tried manual settings,but still no joy.
do i take it that this router cant handle all 3 at the same time then?

thanks

sway