For those not familiar with the National Register of Archives site.
You can search on the county name and get a set of alpha results pages which
will tell you where particular records are held.
For Cardiganshire there are 713 records when using the Places search box
There are 3 other search options to play around with
For more info the NRA's FAQ's are here
Genuki Wales http://www.genuki.org.uk/big/wal/
Help Page http://home.clara.net/tirbach/hicks.html