It's been a while since I played with vortex, but the top main menu is probably one of Andy's custom jobs. Your should find it in the template folder (Probably called splitmenu2.php or something like that)
There is no way this menu can influence the other, no matter what you do with it.
Your best bet would be to hack the current top menu (splitmenu2.php??) to give it more levels. The third and fourth levels to be output to the left module position. You should study the original splitmenu.php to see how Andy does this.
If you manage that, i'll be willing to pay quite a bit for the mod, and i'm sure there are others here who would do the same, including Andy himself