You do need two revolvers. You also need a rifle and a shotgun. For advice on revolvers, read this recent thread:
http://www.thefiringline.com/forums/showthread.php?t=202355
For rifle advice, read this thread:
http://www.thefiringline.com/forums/showthread.php?t=199852
Rifles must be pistol caliber, lever or slide action, with an exposed hammer. The most popular for cowboy action shooting (CAS) are the Winchester 1873 and 1866 replicas (made by Uberti and imported by Cimarron, Navy Arms, Taylor's and others), and the Marlin 1894. Other rifles you might see include the various 1892 Winchester replicas (Browning, Rossi and others), and the Winchester 94. The Winchester 94 is a poor choice for CAS. Most recently, a number of companies (Taurus and USFA, for example) have also started reproducing the Colt Lightning pump rifle, but I haven't seen them show up in competition, yet.
For a shotgun, you need a double barrel (side by side) in 10, 12, 16 or 20 gauge, or a Winchester 1897 pump (12 and 16 gauge only). Good doubles for CAS run around $300-500 and come from the likes of Stoeger, Remington (the "Spartan" line), TTN, Charles Daly and others. Good original 1897's can still be found for the price, or you can buy a modern repro made by Norinco.
