in europe is going to be a pain in the ass to get hold of them. you could wait for them to come on to ebuyer, but europe always has to wait a while compared to the USA. you could import it from the USA, but at no small cost, i'm not sure how the exact numbers work out, but probably at about 100-200 euros more
best bet is to wait
860M will run almost everything at high or better for current games at 1080p, and probably medium for any further graphics advances, even with the new directX 12 coming soon
870M will guarentee everything at high and the majority at ultra or better at 1080p
both should be good for 3-5 years at 1080p and much longer for lower resolutions.