Any recommendations for 3D printer below $2000USD?

[curious aardvark]

Is polystone an actual filament that exists ?
There are filaments that have stone dust included - but I've not seen a polyurethane one.
Ninjatek seem to be doing the most with polyurethane based filament.
What you probably would be better off using is laybrick: https://www.youtube.com/watch?v=cOkt9o4h6C8
Most specialist filaments with included non-plastics are pla based.

Also you can get filament that is coloured with aluminium powder - but it is still plastic.
To actually print metal you'll need to up your starting budget to around $100,000.

The important question - does it need to be fully built or could you handle some basic construction. The more expensive 'kits' tend towards simply bolting a few pieces together rather than a complete build - and with that type of kit you will get considerably more bang for your buck.

There are some truly amazing 'kit' machines in your price category.
What would you consider to be the minimum and realistic maximum build volumes you'd like ?
for $2000 you won't get a metre cube - but you could probably get 600mm

At the smaller end you'll have to go a long way to beat the new prusa mk3: https://www.prusa3d.com/original-prusa-i3-mk3/

Unfortunately prusa don't make larger machines.

worth looking at a delta as well. Not so much for width, but awesome for height: https://tevo3dprinterstore.com/produ...3d-printer-kit