Is there a possibility to skip checking playlist on start? It takes too much time, but it's for me completely unnecessary. I can't find how to disable this option in settings. It could save a few seconds and it will increase system boot.

I hope someone will know the solution

What Amarok version are you using? I thought the issue with long startup times when there were lots of playlists stored had been fixed.

disabling not used plugins should help decrease startup time

But it seems to take me 10secs (or so) to start with 25k tracks and most plugins disabled

I use Amarok 1.4.10, starting takes me about 10 seconds (MySQL) and all plugins disabled, but I was thinking that, I can boost it quite more. Because my system boots in 15 seconds + 10 seconds Amarok and it gives 25 seconds
But is there a possibility not to check existence of every file? Can Amarok assume that every file is where it was before I closed amarok?

Amarok 1.4.x is no longer supported. The current version is 2.4.3 - you are a few years behind!

If you meant 2.4.1, then yes, back then there was a problem with all playlists being checked every time. This has now been fixed.