Hello, OC, from Pasadena,
I would sell before I buy. You can rent in between. I assume you know that when you have a larger home, you not only have a larger mortgage, but larger insurance premiums, tax bills (this can be huge thanks to Prop 13), pool bills, landscape maintainance bills, housecleaning bills, utilities and so on. Right? It's also much harder to find your glasses or cell when you laid them down. lol
Of course, in OC, $1.4M isn't all that large these days. So first, I would do what dames do--window shop. For homes. That way, you'll know a really good deal when you see it. Avoid OC's most common epidemic--Fear and Greed Syndrome. Don't ever fall in love with a house.
If you can "probably afford" two mortgages, you might think of renting your existing home out. If there is a problem with the rental payment, you're covered. But don't rely on a renter to protect you from bankruptcy.
I'm not you, but if I were, I would window shop for a year, meanwhile selling my home.