Bonnie,
The main question to ask yourselves is do *YOU* want a second dog? Chip looks to you as his pack so from his perspective, well I don't think he is lying in his crate night wishing he had another dog to play with. That's something we project on them.
Having said that, corgis do work well in pairs and you get double the entertainment. Chip would do well with a "sibling." Male or female? I think either one would be fine. If you get a girl, just kind of accept now she'll be the "boss." By boss I don't mean she'll be aggressive or scrappy. The bonding issue, Chip will be old enough and already secure in his place in the family. Generally two puppies bonding to each other instead of with the humans is in cases where people get littermates or add a second puppy within a couple of months of getting a first one.
You'll be great with a second corgi, if you decide to go that way.
Debbie