Do I smell Xmas budget?
You should not have any problem getting a decent NEW setup for $700. However, since your feet are probably still growing, you may want to consider used boots if you can find a good deal at a ski swap. Most of the swaps are done by now, but there are still a few left (e.g. Nov 10-12 at the DC Ski Expo in Chantilly, Va) that may be worth a trip. For $900, you could walk into almost any reputable ski shop, let them do the hard work of picking the right gear for you and walk out a happy rider. Some of the online shops (e.g. The House) could probably do almost as good a job over the phone. I have a list of places to shop online
on my web site.
At your age/level of skill, simply keeping your board in good shape and improving your technique (which is going to be happening almost automatically with every trip) will make much more of a difference than what board you're riding. There are hundreds of boards/bindings/boots that could do a good job for you. While some may be a little better than others, you should be basically looking for:
1) Boots that are comfortable
2) The right length and width of board
3) A good price
If that $900 is a "budget", consider spending $700 on gear and saving <$200 for tuning stuff. Take a trip over to the tuning section of this website and see if you're also interested in learning how to take care of your own gear. For a little over $100, you can get a board vice, a wax iron, some scrapers, wax, and files/edging tools and do your own tuning. You'll be amazed how much better a freshly tuned board rides. Man made snow wears down wax very quickly and the better you get, the faster you will wear down the sides of the base of the board.