I am in a similar... Predicament? xD No where near that much $ though.

But with $15k I'd make sure I had quality racks first (if you plan on breeding soon a hatchling rack wouldn't be a bad idea to get while you have the cash) and a good incubator if I planned on breeding that year. And any other necessities (bedding, hides, food) Then I'd start looking at what to get.
But I def would want a Suma, though I'm not sure what they are going for right now. But it seems like a good substitute for a super black pastel for me (haven't heard of any problems with the Suma's and genetic deformities. I'd also invest in some newer or rarer morphs (specter, leopard, orange dream are some of my favorites)