Need power amp suggestions for ProAc Response 4

As far as I know ProAc Response 4 is not easy to drive. Any power amp suggestions will be appreciated. Thanks.
I have heard the Atmosperes m-60s on the 3.5s and was impressed.If more power and transformers are of interest,The Innersound Tube amp at 150w/ch.For Solid-state,the Edge or Gamuts.Maybe a used Lamm M1.1/2.1.What budgetary restraints are you working with?
My budget will be around 10K for a used one. I prefer a solid-state power amp, since I have a ARC Ref II preamp already. Thanks.
I understand that Edge gives a discount to customers without local dealers.The Edge NL-10 monos {225w/ch} at 13k {list} or try contacting Bruce Jacobs {Sound World:920-733-8539}.My friend bought a set and couldn't be happier.
Thanks for your comments, Tpsonic. I am going to use Pass Labs X-600.