The stock sound was garbage eh?
Depends what your taste is but EX15AP is very close to Harman. I actually sent a pair of mic-less version to Oratory1990 who measured them link
My only complaint on the stock sound in contrast to more expensive stuff I own is
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I had to go through 3 sets until I got one with basically perfect channel balance, others were all louder on right side by 2dB which is unacceptable regardless of price.
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Is mostly the bass, as you can see in the linked measurement and EQ profile, it’s starts sloping up too soon. The other only real issue is the ear canal resonance which means that where he boosted 6.5k (because on the measurements it’s where the EX15 is recessed or starts deviating from the target) I lowered 7k because it was too loud and made things sound metallic.