http://www.rideau-info.com/photos/mythdpi.html#top I kinda get ppi's n dpi's more or less. I know the more pixels the better.

I know gimp will max out at about 4000x4000 pixels and MS5 will max out at about 30,000x30,000 pixels .

I'm wondering what corel paint ,photoshop ,paint tool sai etc etc will max out at.

My version of Photoshop (CS5) hits the wall at 50,000 pixels at any one dimension.  I was making some panoramas from stuff I'd shot in Death Valley and was disappointed that some of them had to be split in two.