The fork that's posted on the Niner is made by Pace.

https://www.pacecycles.com/productlist.asp?catID=2

I know a couple that ride with them. One is on a Niner and the other is on a full custom Moots 29er. The guy on the niner swears by his, the guy on the Moots was just riding it and his bike for the first time last weekend with us. Inital impressions were good. You can read about his Moots here: http://forums.mtbr.com/showthread.php?t=204319 but you'll need to be a member of MTBr's forums to see the pics. As good as the pics look, it looked even better in person. Super nice guy.

I'm not sure how much cheaper from you're budget you can go and still get sub 20. Most SS I know usually come in around 23-24, some a bit heavier with suspended forks.

One benefit to running a 29er frame is you could potentionally run the same bike for both road and off road with two sets of chainrings, cogs, chains, and tires. All in all that's about 30 minutes of swaping parts and having a beer while working.