i have 4 dealers around me and NONE will give ANY discount period. if you can get that much of a discount you should buy out your dealers stock and resell them!
i was at one dealer and witnessed a new Signature package being purchased. it was over $20k and the dealer gave him NOTHING off even after the guy threatened to go elsewhere.
so don't bank on any discounts. i have been watching out for Rosenut Sub 15's or Sub 12's but haven't found anything used or demo'd.