The acpistat output is meant to be read this way:
1) Hopefully all (relevant) drivers have ACPI suspend/resume support. In that case, you would not need to load APM.ADD.
2) If one or more drivers neither support ACPI nor APM suspend/resume support, the acpistat tool will tell you "This system will not support suspend/resume as configured." if you have properly loaded APM.ADD.
3) If you do not load APM.ADD you will instead get the "Failed to communicate with APM.ADD. Results may not be accurate." message. Of course, in that case, the APM suspend/resume support will definitely not work even if the drivers report that they would support the APM suspend/resume method. APM.ADD is a mandatory component to support APM suspend/resume.
So, if you get ""This system will not support suspend/resume as configured." that will tell you that you have set up everything correctly but unfortunately, there is at least 1 driver that does not support suspend/resume at all (neither ACPI nor APM). Don't ask me what drivers acpistat picks to examine suspend/resume support, obviously it does not query each and every driver but only drivers that it claims to be vital to support suspend/resume.
You can now go ahead and still try to suspend/resume but as others have pointed out it is likely to fail. On my system, I can drive it into suspend but it will never wake up again, no matter what I try.