Unless you install a direct vent insert into your fireplace, which is expensive and probably overkill for the climate in southern California, gas logs will send most of the heat they produce up the chimney. DO NOT let anyone talk you into a ventless system. They should be outlawed all together, and building codes in many places prohibit them in sleeping rooms. Without a vent, air quality in your indoor space is adversely affected; fumes build up and oxygen is depleted.

You might look into the Eiklor brand of vented logs. When we first shopped around before deciding on a direct vent insert, we were most impressed by the Eiklor logs. They produce the most beautiful realistic looking flames, and they have more gas jets than most, which will probably run up your gas bill. If you call their 800#, you might get Mr Eiklor himself to take the call. Because they produce a bigger flame, they probably will throw off more heat into the room, but most of the heat will still go up the chimney. Check out the Eiklor website.

If you are intent on really producing some serious heat from your fireplace, a direct vent insert is the way to go, but that will run you at least $4000 installed.

Good luck

Thanks Haus-
Maybe what I'm talking about is more like a blower unit that fans the heat from the gas logs out into the room. Just in our case for a more cozy feel instead of just the illusion of a burning log.