The loan goes to scythargon for this (the answer in this thread remained in the comments to Kristof ), and since he did exactly what I needed, I decided that he deserved his own answer.
virtualenv virtualenvwrapper -p, Python. {virtualenv_name} :
Python 3.3:
$ mkvirtualenv {virtualenv_name} -ppython3.3
Python 3.4:
$ mkvirtualenv {virtualenv_name} -ppython3.4
Python 2.7:
$ mkvirtualenv {virtualenv_name} -ppython2.7