And therein lies the problem: Finding a ski that works reasonably well on both backcountry snow and groomed tracks. It's not easy, as the differences in the two snow environments create a dilemma roughly similar to a bicyclist trying to find a bicycle equally adept on smooth pavement and rough singletrack.
But it can be done. The tradeoff is that you'll need to favor the backcountry side of things, settling for a ski that's a little less ideal for tracks. But it doesn't have to be a big compromise. Salomon, for instance, makes a ski called the Snowscape 8 ($179; www.salomonnordic.com) that's designed for people such as yourself. It's moderately short and wide, so is easy to control off-trailbut it's not so fat that it won't fit into a groomed track. And it has an easy-maintenance base that works under nearly all conditions. On the downside, it lacks a metal edge, which can offer a decided advantage on hard-packed or icy conditions.
For that, you need to move up to a ski such as the Fischer Outtabounds Crown ($295; www.fischerskis.com). They're going to be wider than the Snowscapes, so won't fit as well into tightly groomed tracks. But I think these will do you proud.
More length equals more float, of course, so for you I'd recommend the 189-centimeter skis. For your fiancé, the 169s.
Read the Top 10 Cross-Country Guide from Outside Online's partner site, GORP.com, for the best North American Nordic centers.