-- Last Updated: Jan-25-13 2:58 PM EST --
Stacker is just a relatively vertical support that you lean the kayak up against, then secure the kayak to the stacker element and the horizontal cross-bar. It has the same function as saddles or J-bars - in all cases they affix to horizontal bars and the kayak affixes to them. You can put this kind of arrangement, bars plus saddles or stackers or J-bars, on a trailer or the roof of a car or over the bed of a truck. In a trailer made for kayaks, the supports are already built in so you just need straps and any padding.
Exactly how you do it is as varied as your imagination and interest in constructing things from wood vs buying someone else's system. Plastic kayaks are more abusable than composite ones, but that's just a matter of whether you add some padding. Pipe insulation can make excellent padding.
I would caution you on one thing because of where you live. At least up this way, there are some highways that limit access to vehicles with anything in tow. I'd check out your likely travel routes to make sure that you aren't cutting off any options.
Also, I would STRONGLY suggest that you go out and demo some single kayaks before you make a final decision. I have known a number of people, including my cousins and a kayak store owner in his 30's, who trashed their back loading and unloading heavy plastic tandem boats. And because of the price point, these are the boats that most people first gravitate to. If you guys demo, you might find that you both enjoy better fitting single boats and will have an easier carry.