Brett,
Go with the singles... Check the picture in my library, that is an 18 foot, kevlar Perception Eclipse. Awesome ocean boat. Look at the size though, Imagine trying to throw a tandem up there. My darling wife loved kayaking when we tried a tandem, why you ask? Simple !!! It was beautiful just riding along while my silly a$$ paddled her around everywhere. So yes, one person will always work harder than the other. In a single.....keep up or paddle alone !! That being said when the other person gets tired of kayaking or comes to terms that it isn't for them you can easily sell one of them, and buy mods for your ST ! ! ! ! ! If you get the tandem, well you're hosed. All in all good luck. There are places that have tryouts, where you can go and see what "fits" you the best, try going to your local outdoor place and see if they have info on where you may be able to test drive a few models.
Either way its a great sport, enjoy!!