Hard to answer both questions. Would that catchy name be for a company you were starting? I could see someone buying the name if it's very catchy but it's hard to determine without knowing the name. On the other hand, you're only risking like $8 and could make a lot more if you're right about the name.
Second question depends on the name. If you can find some nice .com unregistered and .net then I don't see why you shouldn't register both. If the .com is just okay and seeing as .net sell for a lot less, then I'm not sure it would be wise to get the .net
Hope that helps,
-Addy