Personally, i would go stock, or quietest muffler around.
Did a quick YouTube of 4.7 4Runner exhaust (same as my 4runner), and if i was to get something, i'd get the quietest Borla or Flowmaster, then Magnaflow, then Gibson. Would do single exit, no flashy tips or crazy stuff. Maybe chop off the big exhaust rear end i have on mine. Some new headers would pair nice too.
What's wrong with you exhaust?