Avoid Bushmaster, as has been advised. S&W, Palmetto State, Aero Precision, and some of Rock River would be my go to basic guns. BCM makes high quality guns as well, just at a higher price point.
You said you want an EBR. Other than optics, what do you want on it? Better stock, quad rail or key mod rail, upgraded trigger, sling, muzzle brake/flash hider, iron sights? Barrel length? The M4 is 14.5 inches long and a SBR which requires a NFA tax stamp. 16 inch is the minimum non-NFA length. Other common barrel lengths are 18 and 20 inches.
Optics will be your biggest add-on cost. Decide how you want to use your EBR to decide what family of optics to use. Short range, home defense will be well served with a red dot-type sight. Shooting/hunting at 100 to 400 yards is easy with low power fixed or variable scopes. Beyond 400 you will want more magnification, say 8x-10x. Unless you plan to do precision shooting, you probably won't need more than a 10x scope, which should get you to 800 yards.