I used Crunchbang for one and half years and all this time it was booting to cca. 110 MBs  on my 32 bit machine. (Standard OB + tint2 panel.) I have to suppose you must have done something rather special to fatten this to 500.
Since then I tried setups that let me choose between OB (with tint2 or xfce4 panel) and Fluxbox (with its own panel) during login, under Vsido and LinuxBBQ. The usual difference is cca. 30 MB, so my experience is that FB is ligther indeed, but not that much.