Looks like some pretty good options out there. Components vary with daVinci using Tiagra shifters and Comotion's & Santana's suing 105. While not top level when I have ridden 105 and Tiagra for short distance they seemed to function well.
If you're willing to go one more step down in Shimano's componentry hierarchy, the KHS Tandemania Milano comes with Shimano Sora for a suggested retail of $1999. In the last year or two, Shimano upgraded Sora to 9 speeds and the standard Shimano-style shift lever (as opposed to the thumb shifter they used previously on Sora and currently on lower end shifters). That and the disc brakes I think make this a pretty good value for the money.
If these prices are a bit too steep for a first tandem, take a look at what is available in the used tandem market.
The new issue of Recumbent and Tandem Rider Magazine lists about 25 used tandems for sale, including standard, recumbent and even a couple of 3 seaters at varying price ranges.
Used is not a bad way to give tandem riding a try.
Pedal on TWOgether!
Rudy and Kay/zonatandem