Berkovitch, who has signed a five-year contract, broke off training with the Israeli national squad to travel to London to seal the deal.
Impey, an England Under-21 international winger, has signed for four years - and QPR could yet net a further pounds 200,000 if certain criteria are met.
West Ham's managing director, Peter Storrie, said Berkovitch also held talks with Tottenham before choosing the East London club. "It involved a mad dash to Heathrow but it was well worth it. It was very secretly done," he said.
The Hammers' manager, Harry Redknapp, said: "Andy Impey was training with England not so long ago and is a player I have admired for a long time because he has pace, strength, and he can get by people.
"Berkovitch is a tremendous little player who absolutely murdered us at The Dell last season."
However, Redknapp virtually ruled himself out of signing Robert Lee, the Newcastle and England midfielder, at least until next summer when the player is out of contract. "A year down the line, who knows what will happen," he said.
Clark joins Sunderland, page 27Reuse content