Besides the following, can you point me to any other good starting points for looking into this option?
pfSense is a free and open source firewall and router that also features unified threat management, load balancing, multi WAN, and more
www.pfsense.org
We identify our choice of the best pfSense box for the money. pfSense has become the standard for open source firewalls and is great for home or business.
www.thegeekpub.com
Lawrence Systems has a decent amount of videos on pfSense;
Video on how to install pfSense;
There are a lot of options when it comes to running pfSense such as;
Netgate Appliance (Company who owns pfSense). Comes with PfSense Plus and is the most expensive option.
Used PC's/Custom Built PC's
3rd party Appliances such as the Protectli
I personally use a custom built pc in a rackmount case. I'm running a 10th Gen i3, 8 GB of RAM, Asus Micro ATX motherboard, Seasonsic 500W power supply and a Q-NAP Dual Port 2.5GB Intel NIC. This is overkill and more expensive.
My go to for friends/family is a used Dell Optiplex with a 7th gen i3. I usually look for a SSD boot drive and 8GB of RAM. You can find these on eBay for $100.00 or less.
FAST Computer, Dell OptiPlex 5050 SFF i3-7100 8GB 128GB m.2 SSD Win10 Pro DVD-Rw | eBay
These Dell computers are fairly power efficient and usually pull between 12 to 20 watts.
After you purchase the computer you need to buy a dual port gigabit Intel NIC (one port for WAN and one port for LAN). Do not use realtek or other brands of NIC as they don't work well with pfSense.
You can usually find a dual port intel NIC on Amazon for about $40.00.
Just be careful as there are a lot of counterfeit Intel NIC's on Amazon. I'm not sure if the one I linked to is Genuine or not but it has a lot of reviews stating it works with pfSense and similar applications.
Once you get pfSense up and running you're going to need an access point for wireless. You can either put your Asus router into AP mode or buy an access point like the Unifi AP's, Aruba Instant on AP's or something similar.
Switching from Asus to pfSense was a bit of a learning curve but once you have an understating it's not hard. There are plenty of videos on YouTube that will help you along the way. I'm not a pro with pfSense but if you have any questions I can probably answer them.