That is fabulous!
I must say that I use PosteRazor for all of my enlarging.. It is soooo simple - you just scan in your picture then import it in to PosteRazoe (which is free btw) and then you can tell it how big you want it to be either by physical size or by percentage. I am going to keep that chart for reference! It will come in handy ;)
http://posterazor.sourceforge.net/