NAT Issues


Okay, so here's the deal. I am setup on a business-class cable connection through a single cable modem, and it is alotting me 4 connections (4 external IPs) at one time. Each connection is throttled at 5mb d/l x 384kb u/l. I have my mac, 3 PCs, an xbox, and an aiport express that need to be networked. I have an AP Extreme also that I was using as a router and to serve the wireless connection. I started out having everyone connected through the AP Extrm, but soon found out that by doing that and by using NAT, we were having a very limited connection b/c we were only using 1 out of the 4 connections (1/4 of our alotted bandwidth in effect). So, I tried to bridge everyone through the AP extrm, and that's where I ran into the roadblock with only having four connections alotted to us (4 alotted external IP addresses). So here is where I am at...I can have the 4 computers connected with no problem, however, I need the xbox networked and with an internet connection due to my Live subscription and Media Center Extender Software connecting it to one of my PCs...and of course, everyone wants to be able to stream over AirTunes, so I need the AP Exp. to be networked to everyone b/c apple doesn't allow a connection outside of an internal subnet yet. So, I've heard of some rumors from friends that there are some options out there that would allow me to use NAT with x number of external IP addresses instead of just 1, which would give me the full potential of my bandwidth and also allow all 6 devices to be networked and connected to the internet. So, here's my question...Has anyone heard of such a thing, and is it software I need, or a new router. Any pointers you have will be GREATLY appreciated, b/c the "best of the best" at Time Warner Roadrunner Business Class are like talking to 2 year olds about this stuff. Thanks in advance.