Last week my AKG K99 headphones died; I have been using them for 15 years and despite my best attempts with a soldering iron and new cables one of the speaker drivers is dead and AKG do not sell replacements anymore

I have been looking at two possible replacements but don’t have access to a shop where I could try either of them and can’t really afford to make a mistake when buying them… I am having to wait until I get paid just to think about buying anything! So if any of you have experience with the below headphones I would love to hear what you thought of them. I am looking for headphones that do not colour the sound - just let me hear things as clearly as possible.
I am considering the Beyer Dynamic DT 990 Pro or the Sony MDR 7506. I can’t spend more than the Beyer; I am aware that there are more expensive solutions but that’s the absolute top end I can afford right now. Both seem to have excellent reviews but looking at the frequency responses both have areas that make me slightly worried - the Sony headphones appear to have a strong bass boost, while the Beyer ones have a weird dip in some of the mid high frequencies
https://www.rtings.com/headphones/revie ... dt-990-pro
https://www.rtings.com/headphones/reviews/sony/mdr-7506
I am mentioning this because I have a lot of hearing loss and have to wear hearing aids, so I have a neutral setting on them to help me with music and need to make sure the headphones I have are as neutral as possible. Thanks for your advice!