I sell both Kastle and Fischer, and love Nordica, but don't sell them. FWIW:
The Kastle is fairly stiff, but has a thin core for light weight and is very "light" on the snow. It doesn't have the damp, powerful, move snow out of the way feel of the MX series. Very lively, quick feeling underfoot, a lot of fun, but gets a bit bouncy where the MX really shines: at rough snow at speed. Of course, it is probably the best AT ski around, and will ski circles around any other AT ski that I have found. It isn't a typical "lightweights" ski in that it is still pretty stiff, just not real heavy, damp, and Austrian. It also tends to shine a bit more in softer snow, as edge hold was acceptable but not at the level of a beefier ski on hard snow. For heavier and more aggressive in-bounds skiers, I think the MX88 is the better choice. For lighter skiers, and those looking for a lightweight backcountry setup that won't let you down on any off-piste situation, the FX94 can't be beat.
The Watea 98 is, in many respects, very similar. It also is a light ski, not super damp, but quick for it's width, moderate stability, and not real aggressive onto edge. It is made for crudbusting and softer snow, and again, isn't super heavy or damp like a Blizzard, Nordica, Kastle MX series, Stockli, and to a lesser extent, Elan and Volkl. It would also be a very good choice, if you like that lighter, quicker more "fun" feel in a ski.
The Enforcer is the opposite: it is closer to the bruiser style of a big Austrian ski; quite stiff, awesome edge hold, one of the best groomer skis in this width you can buy. Also an incredible crudbuster. What it doesn't do is feel light on the snow. Direct comparisons to it would be Blizzard's Atlas, Volkl's Mantra, and Kastle's MX88 (the new 98 is a bit lighter, and may also be worth looking at; it isn't as damp as the 2010 MX98).
At your weight, I would recommend the FX94, Watea 98, or Elan Apex and Spire over the Enforcer. It is a bit softer, much better for lighter skiers, and is incredibly versatile. The Elans walk that line between the heavier, damp, crudbusting feel that some skis have, and the lighter, more playful, bump-able and tree-ski type feel that other skis are. I am 155lbs and found the Elans for this coming year to be close to being a "custom" ski for somebody my size.