I know we can lookup the response codes here: http://developer.authorize.net/api/reference/responseCodes.html
But is there a table or spreadsheet of all the Response Codes anywhere that I can load into a table to do a lookup of response codes so we don't have to store the text of the reason for every transaction?
That's a great suggestion. While we work on adding this to the response code page, you can obtain the file here: http://developer.authorize.net/api/reference/dist/json/responseCodes.json
It's updated frequently, so makes sure you keep it up to date.