Now we are finally getting somewhere.
After calling more than 10 shops yesterday I got a clear answer from one of them:

The will get 30 Sapphire RX 580 Nitro+ 8GB cards in July 5th - so in a month.
The sapphire nitro+ cards are supposed to be good as far as I can tell from doing research on different forums.

Each card will be 339€ which is $382 and quite a lot in my eyes.

Now I guess since I just start out the real question is:
Should I just preorder 18 cards so I can at least build my 3 6 GPU rigs beginning of July latest or would you just preorder 6 cards so I can finish my first rig beginning of July for sure and then wait and keep my eyes open until then to see if other shops might get 570s or 580s in until then for a better price? What would you PROs do in that situation?

Again the goal is 3 6 GPU rigs to start mining as soon as possible.

Any help is appreciated.
Thanks a lot.