Hello Razvanvrs, I am a Proac k6 owner and I use an Accuphase E560 integrated amp with very good results. It has only 30 w per channel (pure class A) but I find it more than enough to get the Proacs singing.
I have also heard the k6 driven by very low-powered Audio Note tube amps and the sound was fantastic. So I unless you listen to music and ear-splitting levels, I wouldn't worry too much about having lots of power.
Basically I believe the ribbon tweeter used in the k6 needs to be matched with a tube or class A to maximize its performance.
Hope this helps. Good luck!
PS if you still want a pre power combo, try the class A ones from Accuphase.