"Stopping down beyond f/8 wastes sharpness"
if you are going for ultimate resolution that is of course true but the demands of the real world often interfere on ideals
"I have considered the 24-70 but concerned that as it's a zoom that image quality will be compromised. I will be printing large prints."
How large wil lthe prints be ? What kind of subject matter? Will you be making single row or multi-row panoramas? How are you processing the files? For gneral purposes the 24-70mm does a good job, especially when you either carefully tune your camera's phase type autofocus system for the lens or use live view. A high quality fixed focal length lens can yield better results but shooting circumstances ( air quality, wind, tripod and head choice (esp. with regard to vibration dampening), cable or electronic release instead of pressing the shutter release on the camera) are also factors, as is capture and output sharpening, use of "Clarity", etc.