(As long as it's v1.5, or one of Dark_Alex's previous releases )
My understanding on this is that you MUST use the files provided in this release (along with the 1.50 / 3.03 eboot's) to create a new DXAR on EVERY PSP this is because
1. The DXAR created is (presumably) specific to this custom firmware (ie you can't use a DXAR you created with the last version).
2. The DXAR has some kind of encoding in it that relate to YOUR PSP and ONLY YOURS, so anyone elses won't work for you.
3. If you're going to attempt it, best doing it the correct way, other wise you risk a BRICK
It doesn't matter where you upgrade from - this is a full installation package.