Thanks for all the great advice guys! I should have noted I have carried an AR with an EO Tech on duty for the last several years. I do like the OE, but probably out of budget at this time. Gischileu thanks for the build list & links! right in my budget zone!
If you have carried one for the last few years........... then WHY on earth would you ask recreational shooters what you should put on YOUR rifle?
Wait; I get it. You carried it in the trunk of the squad car......
If you're asking (You did)

my recommendation is not a quad rail. They wind up being clunky and big for a foregrip. Get a foregrip that is small profile and has holes modular so you can add mount points where needed for a light, bipod, etc.
The quad rail units are also heavier unless you really hunt for one that is light. Midwwest Industries has one, VLTOR has one, and the one I really liked said Sidewinder on it. Not sure who made it.
When you add the clunky quad rail, add lights, add this, add that...... the front of that rifle becomes VERY heavy, and un-fun to carry. Yeah, you can benchtop it and shoot; whatever.
If you intend to carry the rifle..... make it as light as possible. Before you make a bunch of changes to the rifle, shoot it and get to know it. Then, if you have a good idea of what you really feel you can utilize on the rifle, get it and install it.
Adding stuff willy-nilly without experiencing the rifle is just a waste of money playing with adult Tinker Toys.
Last course we did was a night course. I was sick as a dog. (Sick today, crappy coincidence!) 5 hours of that was not bad, but even a stripped down Sport wound up being heavy by midnight. And we went until 2. The most common command all night was "Get the rifle up, then down. Get the rifle UP." Guys with heavy rigs kept going bow heavy, and they had the lights kicking on at the knees instead of in the face. Instructors were having to harass them to keep their rifles in the correct place. All. Night. Long.
You could see who was shooting where. And WHY.
And then I hear people getting different stocks, butt pads, to reduce recoil.
It's a 223. In semi.

If the kick hurts with a stock pad, wait till they have to carry a 9lb rifle around for a day.......