I saw offer 159.90EUR for ASUS HD6870 DIRECTCU PCI-E 1GB GDDR5. Is it reasonable to upgrade my 5770 (207 mhash) to this 6870? (Im using single card system so crossfires isnt any options in future with my current mobo)
I'd personally say it isn't worth it. What I would do is try to buy a used 5830 which will give you about the same hash power and ask if they are willing to ship internationally. If you can pick up a used 5830 for 110 usd (76.8 euros) it will most definitely cost less maybe even by a wide margin.
As a side question for you are all Europeans forced to pay like 20% then Americans? Is 20% even the expected price hike?