If you have both CarQuest and Advance knocking on your door, tell the one that you're doing business with the other. After the buyout, they aren't allowed to step on each other's toes. I do a fair amount of business with O'Reilly, since they're right across the street from me, but most of my aftermarket (about 5k a month mechanical, I don't even want to think about what the body shop gets) goes to a local Parts Plus supplier. I'm one of their top accounts, and they get things to me in 30 minutes or less, all without calling. I can tell the salesmen who actually know the market I serve, and don't try and sell me parts that I'm going to buy from GM. If somebody walks through the door and tells me they have QuickStruts for all the GM cars, I'm going to tell them I get WAY more from GM than I'm ever going to buy from them. Try and look at my used car lot, see how many Fords and Hondas are out there. I'm a Cadillac dealer, I'm selling GM parts on GM cars, and cheap crap on anything else I have.
I have accounts with NAPA (my last call), CarQuest, Advance, three Parts Plus suppliers, and O'Reilly. AutoZone works with my Lexus store, but I refuse to do business with somebody who can't tell me the difference between a torque converter and a catalytic converter (yes, they're that bad around here). The guys at Maxi auto (parts plus) take care of me, and go out of their way to make sure I have what I need, and I appreciate that more than I appreciate a pen and coffee cups. And at christmas they bring us cookies, so I'm not complaining.