earth ground disconnected or not ?

Sure go ahead and then when something happens to the house or your system and you have it inspected and find out that the house isnt grounded properly, then what ?

Lifting the 'Earth Ground' from power cables is common especially with source components. I would only do so if there is a problem like a humm (ground loop). That is the only way I would say it will sound better.
Of course like Riley804 means never disconnect earth ground from your house. Also never add a second earth ground to your homes electrical system unless you tie the 2 together

Well. i dont have grounded outlets in my listening room so i took it from a outlet in the kitchen but they are using the same fuse at least. So its rather easy to disconnect the earth in my case.

From what i have heard grounding give you a better bass and not grounded give you a more vivid sound.

There is no cut and dried answer to this, besides it can be dangerous. So you must know what you are doing. All cases can be different for best sound. Generally it is wise to have your preamp grounded and let ground run to the rest of your gear through the IC-ground. But even this is no safe bet, because sometimes your amps inputs may be isolated from ground. Somtimes you do get better sound letting your entire system float. But sometimes you do not, besides, as Riley has rightly suggested, this can be hazardous. You'll have to experiment and listen and best measure your chassis to ground for stray currents. The less current the better sound generally.

Detlof,
If you use higher or lower values on fuses compared to what is recommended in a cdplayer,preamp or poweramp does that affect the sound quality ?