I can't even tell what SurfTabs does, because the user interface happens to be rather pathetic. There's very little indication of which tabs are currently in use, which you are currently using, and what the hell is in each tab - they just say "Tab 1," "Tab 2," etc.. Why don't you use the native tab control instead of buttons in a line?
If what you are intending is that Firefox will open links to external websites in new tabs, and take you to that tab immediately, simply check "Select new tabs opened from links" and "Open links from other applications in: a new tab in the most recent window"