Ok. $1,000 is a good budget for an upper receiver assembly.
Mega upper receiver: Rainier Arms - Pursue Your Passion $135
I’m only recommending that specifically because it should match the Mega lower you have well. The price isn’t bad.
WMD NiB bolt carrier group: WMD Guns Nickel Boron X Bolt Carrier Group $200
I recommend Nickel Boron (NiB) coated BCGs because they require a LOT less lubricant (they’re mostly self-lubricating) and are stupidly easy to clean.
Rainier Arms match grade barrel: Rainier Arms - Pursue Your Passion $250
.223 Wylde is compromise between accuracy and strength I guess you can say. It can withstand the higher pressures of 5.56 ammunition, but also will be more accurate with both .223 and 5.56 ammunition compared to a 5.56 barrel. I recommend 16" length as it’s a good compromise of accuracy/velocity/weight/maneuverability.
Seekins low-pro gas block: Rainier Arms - Pursue Your Passion
It’s adjustable (which you prolly will never need anyways), and it’s a low profile block so it’ll fit under a hand guard if you wanted one that’s a little longer than 9".
Hand guard is a lot of personal preference. What I like may not be what you like. For example, I like hand guards to go over the gas block, and allow a longer sight radius which allows for more accurate shooting when using iron sights. I also hate quad rails since it’s extra weight to accommodate mounting whatever you want. I like these modular types because you 100% have a top rail, and then you can put a small rail on the sides and/or bottom to mount a foregrip, flashlight, etc… This one would be great (for me, at least): Rainier Arms - Pursue Your Passion $150.
Rainier Arms mini-compensator: Rainier Arms - Pursue Your Passion $50
It’s small, and I know JVG’s used it before and I’m pretty sure he liked it’s recoil suppression. It’s not a flash hider from what I can tell, so it’s legal in NYS. Have Adam pin/weld it to your barrel and you’ll be good to go.
Standard arrel nut - Rainier Arms - Pursue Your Passion $10
Total I listed so far is $795. The rest of the parts will run you way less than $205 easily.
Aside from the parts I listed, you’ll also need:
Gas tube - Needs to be mid-length - $15
Gas tube roll pin - $3
Charging handle -$20 for a standard, no-frills version.
Sights - I recommend Magpul MBUS as they’re cheap and work great. - $90
I don’t think I’m missing any parts. Everything I listed will get you a great shooting, balanced upper.