Do you know much about protocols (ip, tcp, udp etc)? Sorry I have to ask as the foundations of these protocols will help you understand the weaknesses and is essential to perform any sort of good firewall practice.
What sort of budget are you on and will this be a home venture?
There are a lot of software based firewalls that can help you learn the fundamentals like NAT.
In respect of Cisco routers the Cisco 800 Series has the IOS Firewall Feature Set, I have a 1721 with IOS Firewall with 2 WIC slots so you can have a DMZ setup and they getting quite cheap now as the 1800 Series is replacing it slowly. PS. A newer version of IOS for 800 series creates a DMZ interface on one of the ethernet ports. On a higher budget the newer 1800 Series Integrated Services Router is something new and promising.
The PIX is another great winner and a dedicated hardware based firewall but might cost a bit more maybe someone esle can comment, have a look here for some more info on the routers I mentioned.
Now there are other vendor firewalls none of which I have really used so I can't comment but they might be considerably cheaper. Better? I dont know...
Yes, I do know a great deal about protocols as I just completed 4 semesters of Cisco Networking Academy at local university nearly passed my CCNA on my first try (I missed getting it by one question).
As far as a budget, I am looking to spend between $300 - $400 on a hardware device - off course, I would want to pay less if possible. I am just not sure whether I should get a IOS based firewall or a PIX version. Which one is most beneficial for being qualified in this area of firewalls.
How much can I get the 1721 router for? And what important features does the new IOS for the 800 series offer over the one that comes in the 1721?
There was a contractor that configured our company's network recommended getting a little PIX device (I believe he said PIX 515 or maybe 505) for the home and playing with that.
Any further insight in this would be much appreciated.