I have a technical question. If I buy a desktop dac and I connect my Hiby dap (music library/source) with the dac and from there into an amp is it still possible to EQ the music using the Hiby? Is the music although EQed still digital?
There is always variation from DAP to DAP, so you may want to ask on the Hiby thread. That said, when using a computer as a transport, you can still apply EQ in the digital domain before sending it off to the DAC. So, it is possible to do with some DAPs (like mine, I believe) and may be a very common feature.
The stealth version of the Arya is pretty easy to drive from a dap. Even SE. I still ask myself if it makes sense to invest into a Hugo2 (no USB C in 2021???) or Gustard x26/h16 combo or an RME ADI? I understand the benefit of an DAC/Amp if you have an 300ohm headphone....
Amps tend to list wattage in their specs because that's a product of current and voltage, but that overall power rating is not the whole story. Some headphones require proportionately more voltage than current (such as high impedance dynamics), while some headphones require proportionately more current than voltage (such as most planars). Some amps do significantly better with one over the other. In the end, the actual amount of wattage needed by the headphones is usually fairly small, just several mW. Much more important is HOW the power is delivered. Not just whether it tends towards delivering more current or voltage proportionately, but also how cleanly it can deliver that power, with how much distortion and what kinds of distortion, how effectively in handles abrupt changes in output, how well it is grounded and isolated from mains hum, and so on. Desktop rigs have a huge advantage in achieving good results in those areas simply because they do not have to deal with certain engineering issues, like miniaturization and power efficiency, that DAPs must deal with. Often they can also entirely omit features that people see as critical in a DAP (like screens or wi-fi connectivity). Because of that, your money goes further with desktop gear. At least when it comes to pure sound quality.
Of course, how much of a priority that is to you is something you'll need to decide. Personally, I found it worthwhile to spend a silly amount of money on a DAC and amp, even though I don't recommend that approach to everyone. It simply isn't necessary to spend that kind of money for excellent sound. Instead, my recommendation is: get your ears on something reasonable and start there. Whether you own it or just demo it, that should settle the question of whether it's worth it to have an amp once and for all. And, it should give you a sense of what you want to get out of an amp.