>>106342118
I don't know about the HE-5XX since I've never tried it. I think it's based on their Deva so it's probably not great. Sundara is one of their best models since it's fully metal so won't fall apart as easily. E10K outputs 200 mW at 32 Ohms and Sundara needs over 300 to reach 94 dB SPL so it's true they might be underpowered running off of that.
>>106342107
More or less. But if long lasting is your number one priority something from Sennheiser might be a better idea. Unless you mean it's the earpads that disintegrated. Then maybe don't get Sennheiser.