I wanted to post some information here to try and be helpful to the open source community. 

Through much testing and much time I have had with this fine open source router. Resources here and online have been helpful however very little information when it came to Xbox Live on here.  I figured why not help my fellow gamer/open source fan.

Setup

WNR3500L and 4 wired xbox 360's

#1 out of the box with the Netgear firmware worked Open Nat.

#2 WRT  - I went right to Kong build 1500 Open VPN - Moderate  Nat 

I tired everything here upnp really isn't working for me on live.  Plus the manually handling the port forwarding wasn't correct I would open Nat and then they would close all of a sudden.  I believe i remember finally reading the kongs build of WRT had upnp problems.  Across four 360's you can't just DMZ each IP they never support more than one DMZ.  

#3 Tomato Open Nat once Upnp was enabled.  Never any problems on any 360 once enabled.  

I did however notice an improved network bandwidth when it came to media center and kongs build. Especially with HD and mkv formats.

I realize looking up that this looks like a rag on Kong build in fact that was not my intention he's build is great however functionality of xbox live is rather my prioirty in the household I have teenagers and my own halo addiction to feed.  

Z