Advice-
Well, I guess you'd have to start with what you like personally.
2000-2005 will give you a pretty broad range of body styles too.
Not to mention the differences in interior types, and exterior styling from LS, LT, and Z71 models.
This link had several good photos of different year models of Tahoes.
http://www.motortrend.com/used_cars/11/chevrolet/tahoe/index.html
I personally love my 2004 Tahoe. I bought it from a private dealer in DFW, and it was (and still is) immaculate. I saw LOTS of used Hoes at big dealerships that were ragged out, and they wanted top dollar for them. The one I got is a 5.3, 4x4 with leather and quad seats. I got it because we had a baby, and the 'ol pickup got too tight on trips. I really did not need the 4x4 since I live and drive in the city, but it's better to have it and not use it than the other way around. The first thing I did was get a K&N intake, and the second was replaced the running boards, and got some all weather floor mats. Beyond that, it's exactly how I bought it.
There are so many mods you can do to a basic Tahoe, but I think it would be best to get one with as much stuff on it as possible up front... especially now that prices should be down on them due to the cost of gas.
Hope this helps a little. Everyone here has some really sweet rides, so there's lots of advice coming your way I'm sure.
BH