Any thoughts on parts that I should change up? I'm wanting to stay around the $800 range, but it wouldn't be the end of the world if I payed a bit more for better quality parts or the like. I get a pretty good employee discount on everything apart from the stripped lower, complete upper, and buffer kit, which I'll have to order online.

Would you change anything if you were building an ~$800 AR?

Total: $805.80
Spike's Tactical Lower (Multi) Forged- Honey Badger ($89.95)
BCM Standard 16" M4 (SOCOM) Upper Receiver Group w/ BCM BCG and BCM Gunfigher MOD 4 ($508.99)
Anderson Manufacturing Mil Spec Buffer Kit ($32.50)
DPMS Lower Receiver Parts Kit (43.24)
MagPul Stock MOE Collapsible Stock Mil-Spec ($25.65)
MagPul MOE Carbine Handguard ($15.33)
Hogue OverMolded Pistol Grip ($11.48)
MagPul MBUS Flip-Up Rear Sight ($35.76)
MagPul 30 round PMAGs x5 ($42.90)

EDIT: I'm also wanting to invest in an optic, any opinions on eotech vs aimpoint or recommendations of more budget optics?

The primary arms micro dot is considered one of the best budget rds on the market. They even have a 50k hour model.

For 800 i would be happy with that rifle.
If I could scrounge up another 200 I'd opt for the kmr hand guard. An ALG ACT or QMS trigger is a nice addition. PSA sells em in a LPK that only costs $10 more than mil spec. I would also rather have mid-length gas, a little more handguard to hang on too and a little easier on the rifle, not a deal breaker if you like the look. Plus 1 on the PA microdot. Some other optics that I like on a budget are Vortex and Lucid.  If weight is a concern the PA microdot can't be beat.

Personally, just about everything.  I also don't know where you're seeing those prices on MOE bits or the Hogue grip, but those are far lower than what I've ever come across.  And don't forget shipping and transfer fees.

BCM is good to go, but there is no good reason to buy a 16" gun with carbine gas unless you plan to shoot Tula .223.

If you're sold on BCM, I would do this , then cut the FSB off and finish it with a UTG Pro 15" SS hand guard.  But you're looking at $750 on the upper alone to go that route.

Right now, today, I think this upper from PSA is pretty hard to beat.  Throw in an $85 BCG and charging handle combo from DSA, you'll be at $546 after shipping on your upper.

Then I'd go with this lower build kit on whatever lower you choose.

Just finish it off with a set of MBUS sights, and you'll be at about $820 shipped.  Regardless, you definitely should think about a FF hand guard from the start, and you will also quickly realize that you should have sprung for the CTR stock over the MOE.

I work for MidwayUSA and I get a good discount on our products.

Thanks for the suggestions! That PSA upper looks like a pretty good deal and I'm definitely considering it.