I am considering the Aprilia RXV because of its power potential. I rode an RXV 550 and it has more power than my Husaberg. More power can be made from the Husbarg and it is no slouch, but I think the Aprilia has more potential.
I have not ridden any of the snowbikes, but from my research into getting one, power is a big factor. Naturally you don't want a big heavy bike either, but snow robs a lot of power.
The downside of the Aprilia is that it is a more finicky engine that requires more maintenance - you certainly want to get a later year, after about '08 or so they seemed to have gotten many of the bugs out.
That said, I think the Husaberg would work well, but I would not put an Explorer on it, I would go with the 2Moto or maybe the new Timbersled. I would not use any kit that used the stock swingarm and shock - they just are not made for those kinds of loads and stress, and they are not inexpensive parts. WP or Ohlins shocks are easily about $1K and that is not even taking into consideration any damage to the mounting points.