The audio equipment in your store does not specify the basic audio specification like frequency response.
Also, "SoundBuds Slim cannot be recharged by most portable chargers because a minimum output current lower than 100mA (0.1A) is required" quoted from the store, could you specify the highest current required (also voltage)? Does it means the soundbuds cannot be charged via portable charger? how about your portable charger? does it not charged at all, or not fully charged?