Interesting question. I've asked it before elsewhere in the form of "if all your current guns were lost and you got an insurance check for the value, how would you replace them?"
I like the ideas about a good, large safe and top-quality reloading equipment. Definitely good suggestions. With a Dillon 1050 costing $1500 and a bullet feeder being another $500, I could easily see dropping $5k of the $20k into reloading equipment alone with complete heads for .45, 9mm, 5.56 and 7.62 and the associated stands etc.
Another $2k minimum for a good safe.
Then it would be a trio of Noveske N4s (assuming they eventually come out with a 10.5) which would run right around $10k for the trio with accessories and optics, oh and a can.
That leaves $3k, which I'd likely spend on a few Glocks in various sizes/calibers. A trio of 9mms (17, 19, 26) which would use up about $2k with sights and holsters, leaving $1k or so for a .45 or 10mm with associated magazines and holsters.
If I had just a tiny bit more, maybe another $3k, I'd opt for a Wilson Combat CQB fullsize in 9mm and a compact aluminum in .45; one for shooting one for carry.