What percent should I ask off?

[Rouvld]

In August for my birthday Im planning to buy my first rolex. I think I should add that this particular watch is my Grail watch as well. The watch is an 118238 Yellow Gold Day Date. I know it might seem silly and sort of a financially bad move (per say) move but I was going to buy the watch from a TRF trusted seller here but back when I had this idea I was sure of how my savings for the watch would look at this time. I came up with this thought to buy from a trusted seller sometime last year (October or November). But now that the time is close I realized that by next month I'll have enough funds to purchase new from an AD. My initial question is how much do you guys think I can get off of the MSRP? And also what is the MSRP for a new 118238? I've been hearing that retail is 27k and I've also heard that it's 31k. So I'm a little confused about that. I know for a FACT that my local AD doesn't move his PM watches very well, AT ALL. My last visit was like a blast from the past with all the new old stock he had. Knowing this I think that I could get a good bit off. I heard and read that 15% is pretty good for a PM watch. I just want to have a good idea of what to expect when I go in as far as negotiation. The ideas of going through a trusted seller here is still an option as well, seeing as I can get a mint example for 17-19k that would be a good bit of savings and I'm all for that but I'm still a little apprehensive with this even thought the person is trusted here, I just would hate to get burned. Any advice you guys could give me would be greatly appreciated.