I'm not going to get into that subject here, beyond noting that the top row of icons linking to external domains could easily be done using the ez-pages navbar with external links. Check the tutorials for ez-pages, and post in an appropriate subforum or thread for help if you need it.
"I would like to have a few top-caterory displayed as tabs in the header and the dependig subcateory's on the left navigation, how do i preceed ?"
Your original question can actually be solved with Categories Dressing.
Use the categories-tabs bar in the header, and set the "active category" define in categories_dressing_defines.php to hide top categories. Then only subcats (of the currently selected top cat) will show in the categories sidebox. See the readme for more info.
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