Hey, that's cool...
Well, first off here is the XC forum on this site.
http://www.bansheehq.com/forums/index.php?showforum=28
There's not a whole lot of info in there but it would be the "appropriate" forum to ask questions about XC. Don't make another post, this is just for future reference.
www.rockymountainatv.com is a great place to get parts from...they have a lot of stuff in stock and usually will ship the same day if ordered before 1pm.
If I were to go with an XC setup, I'd run a 2 into 1 carb for sure, it helps with low end response and ease of jetting. You're on the right track about the gearing, probably want to go with a 20" rear tire though. I just purchased a set of Maxxis I-razrs and I love them for woods riding. They hook great and won't bite too hard when you want to slide. You definitely want to look into a new suspension, maybe some aftermarket a-arms and shocks all around.
I've never heard of those pipes before, what kind of power range are they supposed to have? (mid-top, top end only, all around) I know you said you wanted to be loyal to that company, but if that pipe is designed for top end power, you'd be hurting yourself running them through the woods. You want something to start making power right off the bat, rather than have a pipe that really kicks in at 7-8,000 rpms. Make sense?
Another thing you might want to look into is a shorter swingarm. That'll help you out with traction and put more of the power to the ground
Hope this helps a little bit!