When you're out to buy a new appliance or power tool, it's only natural to make your local home superstore your first stop. But purchasing a complex mechanical device is not the same as picking up a new faucet or some paint or wallpaper — and you may not be getting quite the same good deal. One more thing: think of big-box stores as retailers, period. If you call in for service, you must negotiate a huge phonetree.Here are some things that you should consider before buying that washer or router at a big-box outlet.