High ISO Shooting (Try it)

I came back from the MIHA event this past weekend with two thoughts.
First, I should have dressed warmer.  A few days later, I'm still trying to kick the cold.
Next, I really wanted to solve the shooting action pictures indoors.  Without flash.
Prior to this event, my idea of high ISO was anything north of 800.  I was stuck in the 35 mm film days.  Was.  No more.
If I left the event with no usable pictures, but a better understanding of the ISO and a slew of shots with different settings for analysis - success.
In the end, I shot a few at 12,800 ISO.  Usable?  I'd have to define the term.  I will say that most of the shots at 10,000 are usable.  I have them as backgrounds on the 23 inch monitors.  Very usable.  Sure, I can see the imperfections.  (I'm looking for them.)  Yes, all things being equal, I would love the same result at 100 ISO.  But, isn't going to happen.  Probably not even with professional equipment.  But with what I am using, 10,000 in that arena can work.
I'm guessing any parent would love to have these shots on their PC, but not the 72 inch TV.  But the monitor is very usable.  Tablets and smaller, very usable.
I'm not sure a print will do well.  And I'm too cheap to throw away ink on testing a 11x14 print.  I'll cross that bridge when I need to.
So for giggles, here is the original shot at 100%.  Noise and all.
The stats: D500, 1/500 sec, f/5.6, ISO 10000.  (EV +2)
This is the original image, 100% background layer.

Using PS ACR Luminance and Detail - 70%

(Oh yea, the dude had to go.)  PS ACR helps a little.  What I've found with ACR, is it does a great job with noise under 1,000.  But this is heavy duty stuff.  I am a big fan of the Topaz AI line, and a lot had to do with this.

That is a lot of help.  It's not perfect, but for me and the pictures I took at this event, it is a lot of help.  I don't know what help a flash would be, but I'm not going to find out.  
I'm not saying everyone's equipment will get the same results.  Not sure the D7200 would do this well.  But I should have tried it anyway, just to see its capabilities.  Could I get this with ISO 8000? Would that mean only 1/200 sec speed?(Reason to go again?)
Great day to find out what lies in the ISOs past 1000.  It's not that scary.