Category Options not displaying correctly????????

Hi All.

i’m using marketpress on my website and need some help.

http://www.pcperfect.co/store/

ideally i want to only have display on the main store page the main categories

ie: I have created an audio & visual category, and not created any products in it. But then created a sub category for monitors, another category for speakers. these 2 sub categories ideally should only be displayed if someone clicks on the audio & visual category, kind of like an expanding / drop menu.

is this possible

Also do you know why there is a gap between the categories audio & visual and monitors??

not sure why it is doing this!!