Both Haye and Adamek have been the biggest challenges the klitschko brothers have faced in a long time but they were/are too small and were/are too light !
Both Haye and Adamek are quality fighters and the Klitschko's beat them with ease, in my opnion you need to be a born heavyweight and have a good reach to challenge the brothers. Both Haye and Adamek were giving up alot of weight and when Adamek got in clinches with Vitali the height/weight difference just looked silly !
someone like David Price in a few years would give the Klitschko's a good challenge, 6ft 8, 245 pounds and athletic.
ps - Im a big fan of Haye and Adamek !