Picked up my MPX today after 8.5 months. I fondled an MCX to look at the folding stock which I think I would prefer and they had a used kate moss stock laying around.
It's well used and came off an illegal sbr that someone pawned. When guy came to get his illegal sbr out of pawn they kept the stock. It's been floating around the store for a few weeks and they didn't want it so they gave it to me... for free.
ETA: based on interweb research it is a sig stock(I thought it was a fake/copy). I scored on this one!
I shot a box of ammo through it and the sig sights are surprisingly nice. Optic recommendation? Not looking to spend big-$$$$ on anything. I guess the big choice is between pistol-size or rifle-size optics. The sig iron sights were a decent height for me, so looking for a similar height optic.