Question about theme padding wrapped in Joomla

[kalldrexx]

Sorry if this is the wrong forum but it has to do with both Themes (mostly) and Joomla interaction, so I wasn't really sure which forum would be correct.

Here's my problem.  I am currently evaluating several themes for my wrapped smf Forums.  I want it wrapped so it stlil has the site logo at the top and the menu to the left.  My problem is the sidebar.

The left sidebar is padded like 20 or so pixels from the border (forgot exact number).  The sidebar is correctly positioned when using the default SMF theme, however most of the other themes push the sidebar all the way on the border of the web browser.  My Joomla theme is not fixed width.  I can't figure out what exactly is causing some themes to push the sidebar out while other themes don't and was wondering if anyone could help me figure this out.