Lets start with the premise that you should have a lander for a singe domain name. This will be the source of many high interest enquiries. But is that all you should have? Should you link it to a themed collection of domain names? I can think of a variety of reasons for this. You could make more than one sale to a client. You could sell a higher value name. If your client can't afford the first name, he could purchase a cheaper one. The first name the client looked at may not be the best one for him.