Please allow me to weigh in on transportable systems. I own a number of sources for multiple use case scenarios, there isn't a single device that covers them all perfectly:
A&K SR35 - light, genuinely pocketable DAP for travel.
Cayin RU7 - ideal for watching videos through a laptop.
Hiby R6P2 / Mass Kobo 475 - much higher levels of performance, and can be used in any room.
Some hobbyists imagine throwing the maximum amount they can afford at a DAP will be the best solution for all circumstances - and much as I'm hugely impressed by say the Cayin N30LE, a source like that comes with drawbacks:
• The N30LE is 650g which is a lot to pick up with one hand. My RP62 + 475 combo weights 725g, but I only ever need to lift the 280 grams of the R6P2 to change songs. I can also detach the R6P2 from the amp anytime for something lighter to carry. It won't sound as good without the amp, but for a 280g device (middleweight for modern DAPs) is still impressive.
• Another factor is price. New, an N30LE is USD $5k to have tied up in one device. Whereas I split my investment between the R6P2 & 475, and so don't have to pay another $5k to upgrade both at once, either can be upgraded independently at different times.
• Third, flexibility. Separating your DAC from your amp is actually a really good thing in some ways, it gives you greater means to tweak your system because even interconnects let you bend the sound in different directions, and anyone who's been in the hobby a long time understands Synergy Is King.
If you haven't owned a portable amp you may wonder why they're worth bothering with, wouldn't an N30LE be all you need if you don't mind dealing with the drawbacks? By all means yes if you demand the convenience of a one box solution & don't mind carrying a heavy brick, an N30LE or 320MAX may well be your source endgame.
If you want to push performance even further... yes that's possible. Those two DAPs do not represent the last word in IEM performance simply because they're heavy and expensive, you can get even better sound by adding a high-end portable amp to either of them.
Perhaps because in my experience it's the built-in amp rather than the DAC stage in most DAPs that has a larger effect on what we end up hearing, though manufacturers encourage us to think otherwise by focusing their product marketing around the latest DAC chip. For them it's probably a easier to generate interest by spruiking the specs of the latest AKM chip, rather than say explaining how they implemented a different amp topography with discrete components rather than op-amps.
The elephant in the room is desktop DACs & amps. If you're going to spend money on a separate amp and be forced to use an extra cable, wouldn't you get better performance and value using desktop equipment? The answer to both is yes, with caveats.
With desktop gear you lose the flexibility of where you can listen. Generally the more you spend the heavier items become, really high-end amps in particular can be super heavy and a real pain to move. So you end up being chained to a desk, which may be fine if you work from home & spend hours listening at the same location each day.
Noise floor is an issue with desktop amps though, as expensive ones are usually designed with headphones in mind. Potentially not an issue with IEMs that require lots of power like Subtonic Storm & Elysian Annihilator, but with others background hiss may be annoyingly loud & distracting - potentially introducing a new selection criteria for your future IEM purchases if you've already invested a lot in a desktop amp you want to pair them with.
Desktop DACs & sources work fine with IEMs, the issue there is most require XLR or RCA interconnects so you're stepping into a different world not directly compatible with your portable gear unless you invest in adapters or perhaps custom-built cables.
If ultimate performance is your goal then desktop gear is objectively the way to go, though then you may start to wonder if headphones make more sense given they can scale even more with expensive ancillary equipment.
Which is why some of us feel transportable IEM systems are an ideal tradeoff between portability & performance. You get superb sound in a fairly small, somewhat affordable package you can use anywhere. More performance or more portability is possible, but then you're sacrificing one for the other.
Apologies for the long post but it's a fairly in-depth subject. Ultimately I don't think there's any wrong way of listening, even IEMs used direct from your phone is fine if you're content - the great thing about our hobby is gives us the flexibility to listen the way we want.
And I'm sorry for everything, I'm drunk...
