That's correct - it's only 104 and 107.
104 is a Cinema channel (there's an extra fee for watching content there).
107 is the only 3d channel available at no extra cost for customers with Choice (or more) packages.
I asked directv many times about channel 103 (n3D). Even today, I've received a message stating:
"N3D (Ch. 103), is still part of DIRECTV’s channel line-up. N3D is available at no extra cost for customers who subscribe to applicable Advanced Receiver Services and have the correct 3D/HD equipment/receiver. While N3D is not a 24-hour 3D network, this channel offers part-time 3D programming. Customers are encouraged check the guide for air dates and times."
But actually they pulled the plug on this channel since July 2012.
However, they finally removed that channel from their channel listing on DIRECTV Mobile site
I hope more 3d content will be added as long as more people are buying now 3d TVs.