I've got the opportunity to purchase a Netscreen 100
from a friend who works for a company who no longer is using it,
at a very good price.

I've been looking at a decent hardware firewall for a while now
and this looks like it will fit the bill nicely.

My current config consists of a basic ADSL router, and I'm making
use of the firewall on it. It's in a flatting environment, so
at this stage, I've managed to hit the wall for the amount of
port ranges that I can open (10).

What I would like to know is, in a NAT situation, how many ports
(or port ranges) can I open to allow access to computers
from the untrusted side to the trusted side?

Obviously I'm going to be needing more than 10 to make it worth
considering buying for me.

The other question is, how many custom services can I create?
Obviously this is equally as important, as I'm going to have
several custom ones to cover the service double ups between myself
and the flatmates.

I've also got the opportunity to buy a Zyxel Zywall 10 from the
same person. The above two questions apply, and does anyone have
experience with both to be able to give a comparison (or even if
you only have experience with one of the devices, could you do a
quick write up on why I should buy it).