Towing 9000# and carrying 8 passengers will require a pretty stout SUV. Look at the 2002-2006 Suburban 2500 8.1L w/ 4.10 axle ratio. The 8.1L and 4.10 will give you the max trailer weight of 12000#. But do subtract from that 12K the total weight of passengers and cargo.
As far as model year differences, 2001 was the first MY for the 8.1L but has the 4L80-E transmission. GM beefed it up to the 4L85-E in 2002. 2003 added the Stabilitrak system and upgraded interiors.
Upgrade any of these GM hitches to a good Class V by Curt for under $250. The OEM hitches are not good.