I recommend the Pentax DA 55-300 PLM or a used Sigma 70-300 DG OS, not the APO model. A few years ago the DG OS was sold for about 140-150 EUR and it's really a nice lens for the buck. It's clearly the best non-Pentax 70-300 and it's FF. It has some flaws too: zooming is jerky and the filter thread is rotating, the corners are less sharp ... but the pictures are really okay. On the other side the OS is at 300 mm a bargain.
Look here for some pictures with 1:1 crops:
DigitalFotoNetz.de :: Thema anzeigen - Sigma 70-300/4-5,6 DG OS