I originally owned CS3 Extended and over the years as I up-graded I migrated to CS6 Standard. I am now motivated to exploring Image Stacking to improve SNR. Obviously, CS6 Standard does not support SNR (Medium or Mean modes) image stacking. I have plenty of disk memory (over 700GB free on my internal drive and a spare external 500GB drive) and 8GB of RAM. Are there any problems with running both versions of Photoshop? My plan would be to perform the stacking in CS3 and then move the file to CS6. I tried to get my question answered by Adobe and after 45 minutes of getting no place, I gave up. I guess I'll just add my name to the huge list of customers who are totally unsatisfied with Adobe customer support.