Just my thoughts. In the marine corps. We were trained to hit at 500 yards with iron sights. That was with a beat up old m16a2.
So your ar with get the job done. The rest is up to you personal preference.
That being said. I ran a leopald vx-r 3-9x40 with the firedot and ballistic reticle. It is an awesome scope. I would leave it at 3x and light up the firedot for close work. It was only marginally slower than an acog or any red dot. The average shooter would even notice a big difference in speed.
Then when want to go out and "reach" the 6-9x will get you the magnification you want.
Im a huge fan of vortex but the vx-r has a special place in my safe as a reliable go to that is my shtf/coyote/do whatever i want to get done rifle. Also i hears aa optics is a great place for refurbs that helps you get the best glass for your buck.
I have spent many an hour at the KD ranges at Camp Atterbury with ILEA's DMR program. I highly, highly recommend the PA 1-8. While you lose a little on clarity at 8x it is still one awesome optic. Factor in the price, it is a no-brainer.
Have you considered saving up a tad bit more money for a better optic? If you're running a SPR I would really recommend a Vortex Razor 1-6. If youre military or LE you can get a hefty discount on some site from them. If not the Razor the Viper Ive seen alot of SF guys run over here over seas.