I recommend buying from Batterystation, their US made CR123's are low cost, reliable cells. Surefire, Duracell, Rayovac, Energizer, as long as you get em from a reputable supplier they're all good. Just avoid the chinese made batteries. They may have improved over the years, but there were quite a few issues with them a few years ago regarding storage life and the ability to hold voltage under load after they'd been sitting for a while.
Battery Junction is also very popular and sells most of the major brands, including Titanium Innovations which I've bought dozens of over the years. Also, you can't generally go wrong with many of the flashlight dealers own brand of 123's. A good example is 4Sevens, as well as EagleTac.
I haven't used the new label Titanium CR123A, are there any changes from the older orange-y label? Either way, they were good to me and the "double set" is pretty cool. They are paired, wrapped in plastic and you can use them in most flashlights just like that.
I haven't needed to buy any in awhile though as I picked up 40 Rayovac from Botach tactical. 2 packs of 20 at $25 each, plus there is a coupon for CPF members.