KEH is great as everyone has said. I've been buying for a decade+.
But there is one thing you need to watch out for: KEH does not (as most used dealers don't) typically thoroughly test all equipment. If they did, they'd go out of buiness. So it's your responsibility as the purchaser to test the equipment after you receive it, and to notify KEH if there is any problem. They WILL take of care of it if there is a legit issue, and they won't rest until you're satisfied (which can mean a repair, exchange, or money back when all is said and done).
Don't let this one (practically universal) caveat dissuade you, though...it's just a fact of life when buying used.