Congrats! What a wonderful choice and opportunity you have ahead of you! 🙂
I've bought all my pianos new from the crate, even though that goes against common wisdom. I did playtest my most recent one before finalizing my choice though. I also happened to get a deal that I was very happy with.
So I think you can do both with a bit a work!
When are you planning to visit the second dealer to try out the SK3? It's not a given that you will like it, but I think chances are good.
I also think the dealer may well be inclined to give you that $3000 discount to help you make up your mind. Faced with a choice of an extra $3000 discount vs keeping the piano on the floor for 2 years, I think that's a no brainer for the dealer.
Try negotiating the price up front but don't sign away your chance to playtest the piano before finalizing the deal. Let them do the prep and tuning. You may end up with the best of both worlds!
I'm also quite the penny pincher from my student days. PianoTell runs for the cost of a cup of Matcha Latte a month. On the other hand, I don't regret one single bit all the money I've poured into pianos and piano related stuff. It's an absolute joy for me.
Even if you don't get the full discount, and you still love the SK3, I think you should still go for it!
Either way, I would love to hear how it goes! Have fun. 🙂