I'm trying to use iptables so that all traffic in on eth0 goes to 192.168.0.25. Like a true DMZ, I think.

the 192.168.x.x network is on a virtual nic eth0:1
eth0 is my out side nic.

To do that nat from 192.168.x.x to internet I do
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

I now need to DMZ to my 0.25 box

Tried something like this no luck.

iptables -t nat -A PREROUTING -p tcp -i eth0 -j DNAT --to-destination 192.168.0.25