I obviously don't know how much the shipping $ would eat into your budget, but if we forget about shipping for a minute then $3k gets you darn close to the cost of a roundnose superjet, with or without some common mods like the b-pipe exhaust...just for reference I've seen some for $3500 recently.
As far as the kawasaki vs. yamaha thing: they are both good skis...they just had different design goals. If you want a ski that can carve rails around buoys with top end speed, then go kawasaki. If you want it looser, more bottom end, more for freestyle, go yamaha. That's a pretty blanket statement that I'm sure some would argue with, but that's how I see it. Hint: the answer is Yamaha.
As far as the buying from the US thing, I can second that as being "standard practice": my friend recently sold his ski to someone in Canada, and most of the interested people were from Canada. We're about 1.5 hours from Niagara Falls, so I'm sure that helped, but it still surprised him. The buyer reported back that he had no problems whatsoever at the border driving back home.
