Amiga 4000 MhZ <-- As much as possible
Amiga OS 5 <-- Or isnt that out ?
Ram <-- Minimum 256 MB
HDD <-- Minimum 40 GB
New White Keyboard... Danisch or English or German
New White Mouse...
Graphics and Sound ... Shall be good 
CD and DVD burner incl. software... 
Must be built a new Tower .. A nice one...
Ehr, you're a bit off with these specs. You are either building a kick ass Classic machine (looking at the 4000), or a poor next-gen machine.
I; myself prefer to love and cherish my classic setup's, the fastest CPU I have is a PowerPC 200Mhz (in my A4000T). I am not waiting for OS4, or even 5 to be released. I will most likely not buy any new hardware; unless it cooperates nicely with classics (maybe a Powervixxen; if there is ever one; or a Dragon). I will never consider buying an AmigaONE or Pegasus; there is nothing about those machines my PC can't do, let alone at that speed.
The Amiga experience for me is; and has always been the tinkering with Hardware, playing around etc.
I never want to; or expect it to be able to; burn DVD's, download large RAR files from newsgroups etc.
But on the other hand; you never know. I sold off all my Amiga's in 1997. Look where that got me; I now have every single model....
BTW: Welcome; you'll feel right at home here... :-D