Your zumo 660 has plenty of internal storage for the CNEU maps - they have actually gotten small in size over the last two years due to better compression.
Firstly, remove the partial CNEU maps you just installed (gmapsupp.img):
-- WIENER NEUSTADT, OSTERREICH, BUDAPEST, MAGYARORSA
-- Western Europe
Then reboot your zumo and make sure your CNEU 2013.20 maps are ENABLED. The CNEU 2013.20 3D are only 3D data to supplement the street data but it needs to be there. Try finding your Budapest location again.