I would go in armed with my comparison shopping and then tell him you will pay no more than the cheapest price you have found and if he won't go for it go buy it where you found it cheapest.
I think the biggest thing with haggling is being able to walk away if you aren't gettting a fair price. But I say this as I live in a big city and ahve the luxury of being able to go somewhere else.
At $2100 I would order it off line before I would pay that price. I paid 1400 with all the attachments and side table in Feb.
Good Luck.