Speedtouch 585 problem - any ideas?

I've just received a new Speedtouch 585 today and I'm experiencing heaps of problems trying to configure it correctly. What I want to do is the following:

Assign a single IP address to all the computers in the house using private NAT/DHCP.
Assign the remaining static IP addresses on my Zen account to my Linux server.

The best I can currently do is either NAT/DHCP for everyone or static IP addresses for everyone.

Going the all static IP route I'd need something like 8-10 of them for all the internet-enabled devices connecting to the router. Given IP addresses are a precious resource requiring justification I don't think Zen will be approving additional IP addresses on my account to simplify setup of my Speedtouch router Nor should they.

The way I used to have this setup was one Speedtouch 510 and connecting a separate Wireless Router to the Speedtouch. The wireless router had a single IP address for all the devices, and my Linux desktop was the only device connected directly to the Speedtouch... making assigning IPs as I needed simple.

Can anyone give me some advice how to achieve what I want? Or recommend a really good setup guide that might help me get this done. The electronic documentation is pretty poor.

Crossposted here.

Yes I posted it in the wrong forum. Please don't shoot me.

Not going to shoot you but I'm sure you appreciate how frustrating it can be for some to read a post, reply to it and then find the same post in another forum where the person has already received responses.