Tomek: the biggest differences with "good" digital gear as compared to "average" digital gear is VERY noticeable. That is, if the rest of the system is capable of revealing such things.
Many of the differences are not "in your face" changes, but mass quantities of subtleties. That is, background noise is reduced. This allows you to pick out more details due to lower volume signals actually being able to be heard rather than being lost in the noise floor. Since there is now a greater variance between the quietest passages that you can now clearly make out and the loudest passages that you could always hear, dynamic range is increased. On top of this, the reduction in noise / "increased blackness" allows you to hear "in-between" notes. This ends up sounding like more space and air around the notes played by each instrument. Music should have a better sense of "flow" since better quality players preserve the "pace" of music in a more accurate manner. This comes across as a cleaner presentation because of less phase related distortions with the proper time and amplitude variations that occur between primary notes and harmonic overtones. I can go on and on, but you get the point.
In plain English, your system is either not up to revealing the differences that a player of this calibre is capable of producing, you lack listening skills or this player was highly over-rated. It could be a combo of all three or just one of the above. My guess is that it is a combo of all three, but to what degree each part of this equation comes into play, i have no idea.
If you haven't already been doing so, leave your gear powered up 24/7 for a couple of days and then give it a listen. Most digital gear takes a couple of hours ( at least ) to fully settle in thermally. If you do this and don't notice a difference and are completely happy with what you already have, you've answered your own question. That is, there is no need to spend any more money when you've already reached the point of diminishing returns. Enjoy what you've got and put some money in the bank and into your collection. No sense in throwing money away on products you can't / don't appreciate. Sean
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PS... My comment about lacking listening skills or the gear that you have was not meant as a personal put-down or "slam" against you. As i've stated here before, most people "hear" but they don't know how to "listen". Listening skills are something that develop over time. Most of it occurs once one is exposed to a good quality system that is both musical and resolving. Until one is exposed to a system of this calibre, your point of reference and ability to discern this level of detail has never had a chance to develop.
This type of "growth" takes place primarily because you've never been exposed to such a high level of reproduction, so you've never really heard how much detail and musicality that you were losing all along. Now that you know what you've been missing, you start to notice these things more often and more easily, which is part of developing listening skills. Previous to this point, you never felt the need to develop listening skills as the differences that you can now detect on a high resolution system never existed on the systems that you've been exposed to in the past.
Like anything else, with enough time and exposure, anyone can become a "pro" at listening. In order to do any job well though, you've got to have the desire, experience and proper tools first. One can have the desire, but without experience, the end result might get you by, but it is probably not exactly the best that could be done. One can have both desire and experience, but with crude tools, the end results may still not be what one had in mind. Until one becomes a skilled and experienced craftsman with the proper tools, you should consider all of this a learning experience. Having said that, some people are naturals. Most of the rest of us had to learn the hard and expensive way. As such, welcome to the club and i hope that you'll stick around : )