November and December should be a decent time to get a better deal.
I was able to get 3k below invoice after utilizing the BMWFS loyalty incentive. Which ends Jan 4.
http://www.edmunds.com/bmw/x3/2016/car-incentives.html
And if you attended the Ultimate Driving Experience earlier this summer, the $1,000 coupon can be combined with BMWFS incentive. My sales checked with BMWFS and confirmed before I signed the paper.
I got mine from NCBMW, but at times Pacific BMW also gave me somewhat competitive quote as well.