CS 6 Khan - Gencon exclusive, normally called GenKhan
CS 7 Khan - USS Reliant (Independent) prize ship
CS 8 Khan - USS Reliant (Federation) retail ship
CS8 is a good general captain with a nice perk. CS6 is a cheap way to get high captain skill since he "matches" the highest skill on the board. He tends to be a well loved captain in the Independent faction in any of his guises.