Does the 60d have focus adjustment? If not then you will have to deal with the inheirent manufactuing limitations of lens and camera. Some will be good and others not so much. If you demand pixel level sharpness in a $200 lens, all I can really say is good luck. It's rarely a case of "this lens is soft, therefore all others of this lens are also soft". Read the outstanding "This Lens is Soft" article at Lens Rental. The other option would be to send both lens and camera to Cannon for calibration. However keep in mind all that does is get the camera in line with that particular lens. If you have other lenses that are currently acceptable don't be surprised when you get the body back that those are now OOF.
My recommendation for what it is worth, buy the lens that fits the budget from a good retailer with a good return policy and try one till it fits.