want to be able to read the WiFi signal to noise ratio to determine if I have a bad WiFi environment.
It would be better off with something like kismet https://www.kismetwireless.net running in a workstation.
May be, you are looking for a representation like this:
Kismet has listed the supported wifi hardware in the above site.
The typical capture is in the order of megabytes every second or even more, depending on the environment.
Omega2+ has 802.11 b/g/n, (5 GHz support is optional in "n") up to 150Mbps as per specs, where as n itself is 54-600Mbps.
Also, there are hardware analyzers that meets the needs of a CWAP.