That rear folding sight, how does that work underneath the scope?
BUIS are for backup not to be used with your optic trying to mall ninja some co-witness baloney. My rifles with quality glass on them don't have BUIS at all, I have no worries about an optic failing (especially since no one is shooting at me). I buy high end optics because I've tried the cheap stuff and it's crap, I won't even run Bushnell any more. Aimpoint or similar for dot sights and Sightron, Nightforce, Trijicon, and Elcan for glass with a reticle. I do like some of the new Burris and Nikon stuff for a more economical optic on certain rifles and even though I'm not a fan of Vortex they do have a few models I like, just stay away from their lower end stuff.
If you're going to buy cheap glass make sure you never look through quality glass, that's how I realized Bushnell was junk. I ran a Bushnell Elite 6500 series scope side by side with a Sightron on a couple long range rifles one day at the range and sold all my Bushnell scopes shortly after.
I also got a good laugh when I traded AR's one day for a couple magazines so a guy could try a piston driven AR and I had my Elcan Specter on mine while he had a Bushnell AR scope and he couldn't believe how much better he could see the targets through mine. I didn't want to shoot his any more after one magazine and he didn't want to trade back.
I realize spending $500+ on glass isn't in everyone's budget and some guys don't get too serious about shooting so high end stuff is hard to justify but you can never go wrong buying quality glass. The thing to remember is that you truly do get what you pay for with optics and you can keep it and put it on your next rifle so spending more on your glass than your rifle does pay off.
OP, I would buy a S&W M&P for $700, a Hi-Lux CMR 1-4×24 from Wolverine or an Aimpoint PRO, and the rest on ammo, magazines, and magazine pouches.
The Hi-lux is in the $400 range, has great glass, zero-stop turrets, and a nice illuminated reticle. They're hard to beat until you get to the $800 mark.