Alright, so I have done a bit more research and I have decided that I'll buy the Sennheiser HD429 (since my store, for some reason, lacks the HD439!
In case somebody is interested in the research that led to my choice, I went here http://linustechtips.com/main/topic/94045-what-to-buy-among-sennheiser-hd-400-series/ and here http://graphs.headphone.com/graphCompare.php?graphType=0&graphID[]=3721&graphID[]=3731&graphID[]=3741&graphID[]=3751&scale=30
Thanks to everybody who answered!