The reason I use the PrC pack is because there are tons of spell fixes in there and it allows sneak attacks with ranged touch spells for my Arcane Trickster. Not to mention a whole boatload of new spells and feats to choose from! It may also fix the spell resistance bug.

Sorry, I am not familiar with the head hak. I had a hard time finding the mod that gives you accurate and better trap descriptions. I use that one too.