What to look into

There are a few things to consider when looking into high-end audio, and I’d like to explore what to look into when getting into audio. Sooner or later those will come into your sight, and I’d like to stress that each of those aspects are important in the long run, but some might be of more relevance for you than others, for example some users might prefer having an IEM that isolates very well from the outside noise, while other users might prefer a more open experience, while others will place comfort on the first place, having ears that will only fit a certain kind of IEM shape (same goes for headphones). 

• Sound quality. First, and foremost, this is the most important aspect when looking into enthusiast-level devices, regardless whether we’re talking about IEMs, Headphones, Speakers, DACs or AMPs. Even Microphones respect this rule, and you should always try to focus on figuring out a few things about the kind of sound you’re looking for.
• Sound Quality – Signature – This is the signature of your device. Most DAC/AMPs are neutral, and most AMPs are mostly neutral, but headphones and IEMs tend to be extremely different from each other in terms of signature. This is usually described by the overall tonality balance between the bass, midrange and the treble, and certain curves have been described before. For example, a warm sound will have the bass and the upper bass enhanced in relation to the midrange, while a V-shaped sound generally has the sub-bass, bass, and the treble enhanced in relation to the midrange. If you’re not sure what kind of sound you’re looking for, it is best to read the review for a product you own, then try to see how it was described, then try to use it as a point of reference when comparing it with other items. 
• Sound Quality – Soundstage – The space and the overall sensation of space created by a device. This one ranges from intimate, which is “the feeling that you’re sitting right next to the singer”, to large or huge, which is “the feeling of sitting in a large concert hall, with all instruments surrounding you”. 
• Sound Quality – Texture – This describes the level of texturization an item has, which is basically how well defined textures are. 
• Sound Quality – Detail level – This refers to both the macro-details and the micr-details, basically small parts of sound that you hear with higher-end products, or with really revealing and well-designed products. 
• Sound Quality – Resolution – The general feeling of resolution is given by many factors, but it generally refers to the overall detail retrieval abilities of a product, in combination with the texturization. 
• Ergonomics. Every device out there will have a certain ergonomic to itself. When looking into headphones, try to keep in mind whether they are foldable, or large and comfy, whether you need them to be, or how comfortable they are. For DACs and AMPs and DAPs, the shape and button placement will dictate most of their ergonomics. For In-Ears, there are a lot of aspects to their comfort, but the largest ones are the IEM inner shape, which can be rounded, or have corners, or certain protrusions that can really affect comfort. The bore width and size, wider and shorter bores tend to be less comfortable for smaller ears. There’s also the angle of the bore to consider, as some IEMs might feature an odd angle to their bore, which may make their usage difficile. The other aspect is whether they are closed or open, which will affect isolation, but also whether they have driver flex, and how they’ll feel after many hours of usage, deep fitting, well-isolating IEMs generally being comfortable for a some users, while other users find their comfort with average-fit, open or semi-open IEMs.
• Battery Life. While headphones and IEMs don’t typically have a battery life to speak about, Bluetooth-enabled Headphones and IEMs will have a battery life, which you need to take into account. Those can vary widely, from a few hours, to tens of hours. DACs, DAPs and AMPs also have a battery life that should be taken into account, and it would be best for any device you select to have at least 6-8 hours of battery life, with 10 hours of more being a sweet spot for most devices. There are rare products where battery is sacrificed for power, and in this situation you need to make the choice according to your needs. 
• Design / Aesthetics. Every device you purchase should look attractive to you, and even if this is not the most important aspect of your purchase, it is best to look for devices that you are comfortable with. 
• Fast, Fluent Firmware. For DAPs, DACs and AMPs, it is quite important to have a fast and fluent firmware, especially if you’re going to use the device for portable usage. 
• Versatility. DACs, AMPs and DAPs need to be able to drive a wide range of IEMs and Headphones to be fit for your daily life and to be fit for a large number of customers. Same can be said about IEMs and Headphones, the less compatibility problems there are for a device, the better that device is in the long run. A more versatile In-Ear or Headphone is one that sounds better with a wider array of music. 
• USB DAC function. For DAPs, DACs and AMPs, it is important to have an USB DAC function integrated. 
• Connectors. It is important for a IEM to come with the proper connectros (2.5mm, 3.5mm, 3.3mm), and for a DAP to come with both HO, LO and Coaux connections to serve a wider range of purposes. 
• File support. DAPs should support a large number of file types, most propeminent being AAC, MP3, FLAC and Wav. 

Here are a few videos and resources that might help you get started better with this hobby, and how to get the best out of every step of your journey