Hi all, simple question to help my understanding..

I am a Pale master, I have a potency item that gives all spells level 6 or lower 50% damage increase. This affects my healing as well from DA, and damage output from necro-skill-spells and of course the glorious FW (not to mention Past life Magic missiles). I'm about to get my last feat and will need heighten for my future hold monster life.

Heighten will bring all my spells up to the highest level I can cast (l9). Will this make my potency item worthless while heighten is on (since I don't have a spell level 9 potency item)? So less healing, damage, and FW output...for the cost of better DC?

Do I understand this correctly? My DC will go up (I may just be casting web and hold monster anyway), but the damage would technically go down? I honestly have no experience with using this meta-magic.

Anyone clear this up for me?