Reputable dealer vs CarMax?

I'm looking to buy a vehicle with cash and am planning to purchase from CarMax because of their return policy, unless there's a reputable dealer out there. Not a dealership, they're all shady.

I don't want to deal with sales tactics or schmoozing, just GOOD customer service. Someone who stands behind their vehicles. Someone who will make it right if I buy a $30,000-$40,000 vehicle and the transmission blows up 24 hours later - but preferably someone who sells reliable, thoroughly inspected vehicles.