Looking around there seems to be quite a lot of windows based sound cards that have virtual surround etc.  I am looking for something that would work for a macbook pro / mac laptop - ideally software based if possible.  I have seen the Beyer Headzone and think that it's £750 I can't justify now...

Running a 2010 MBP from headphone out comparing it with my USB MODI/Magni powering AD 900s, Sennheiser 580s and DT880s.  Apart from the volume difference (Dt880s being the obvious one needing amping, the other two were actually reasonable volumes) it sounds damn good.  Not a huge difference if...