A router offers a very good hardware firewall.
Thats what I'm trying to figure out now. As for invisibility, I'm not a big fan of security by obscurity. Having worked for a firewall company in the past, I am reasonably aware of the shortcomings of certain types of security. I was suitably impressed by the abilities of the hacking community as my employer had in its hire some very tallented individuals.
A firewall on your client PC is not
a good idea. Way to many exploitable services running.
I also want the flexibility of being able both isolate computers in my home from each other and to be able to expose specific ports to the internet should I need to. I see some routers now allow you to designate one port as a DMZ, but from the very limited info available I would guess that the router opens up everything (ie: not configurable).
Noise was the biggest issue with my current firewall. There are three possible options for me:
1. add a notebook dirve or a larger quiet desktop drive.
Unfortunately, this pc will probably only recognize a 20gig drive at the largest, and I hate the idea of 'wasting' unused drive space.
2. buy a purpose built firewall appliance.
There are a couple of consumer solutions out there for around $300, but thats more than I wanted to spend. The one solution that looks most promising would also need mods to replace fans with something quieter. You would think the folks who designed this for consumer use would think about noise as a potential issue.
3. try to set up my firewall to boot from CD and use a usb stick for writing out log files.
I don't know if it is possible to put a firewall on a cd/dvd.
Right now the most expedient solution seems to be #1.