Update: After blasting music out on these headphones for a couple days, the right (newer) driver sound pretty much identical to the left one now. The right driver starts clipping around .5dB sooner than the left one, which is completely fine. All drivers aren't exactly the same, after all. The light fluttering sound that I heard when the driver was new is gone, so I guess the voice coil isn't rubbing against the magnet anymore. So yeah, I'm completely satisfied with this headphone, and it's going to be a keeper for sure. If any of you guys in the future find this thread and have any questions, feel free to post in here or PM me. For the people that want to replicate this mod with other AD series headphones, please beg the parts division to test the drivers before they ship them out to you. That will save a whole lot of time and aggravation. For any of you guys wondering about the first grill (it's all dented up and stuff), it was the first time doing that, and I was experimenting with ways to pop it out. If you do it cleanly, like I did with the second one, you will be able to reverse the mod and have a stock driver again. Just use your fingers and push it inwards. After you pull the grill off, the adhesive is pretty much gone. You'll really have to push it in for it to stick good, so you may want to get some super glue or something and run it across the crack between the grill and the driver to seal it back in place. I just left mine alone because it's not that big a deal for me. As long as you have something covering the grill and you don't throw the headphones on the ground, you should be okay (I've dropped mine a couple times, and the grills are still in tact). If they fall off, just push them back in.
To pop it out, you'll want to get some needle nose pliers (make sure the teeth are in very good condition), clamp the grill, making sure that the pliers aren't touching the membrane, and slowly pry it open. Make sure that you have a very good grip on the pliers. You don't want to slip and screw up the driver. If you accidentally dent the membrane, just get some chewing gum, chew it up, take it out your mouth, blow on it, stick it to the membrane, and quickly pull away. You may have to do it a couple times, or let the gum set for few seconds longer to get some of the challenging ones out. The membrane is more durable/flexible than it looks so you don't have to worry too much.
Unless you're a basshead, and/or you listen loudly, you don't have to worry about modifying the grill. Under normal listening, you should never be able to hear it.
Making these headphones balanced will be next thing I'll do, but it won't be anytime soon.