Well, there are basically only 3 models to choose from, depending on how sporty and fast you want to get and also how much money you want to spend. Although each year that goes by, prices go down for the good ol' E53. We have had ours for 2 years now and love it, but if we had to do it again, I would look for a 4.4. We chose the 3.0 for economy (my wife's car so she didn't really care about more power and speed and sport, etc) but the 4.4 actually gets similar mileage to the 3.0 with a huge bump in power. As far as everything else, interiors are identical with different cosmetic differences (wood, etc) and we don't feel like we're lacking anything in our 3.0. I love the looks of the 4.8, especially in Imola Red, but the wife thought it was too flashy, plus at the time the price jump to the 4.8 was pretty significant. I would go for a black or truffle interior as the leather is hard to keep clean with a light color. We also live in Vegas so cold weather package was unnecessary. We also do not have nav but I wished we'd gotten it to add the dvd/tv playback on it and better display for our ipod and sirius, not sure how the actual nav operation is but we use a portable Garmin anyways. Everything else is personal preference, sport package adds better steering wheel and suspension. There's a lot of E53's out there, just research exactly what you want and look, used ones seem to be taken care of pretty well by their owners. We also got ours in the Southwest region, as well as an X3 my mom bought because they're less beat up by the snow/rain/terrain of east coast. Ours had 25k miles when we bought it but looked brand new, that's one of the reasons we bought it. Good luck with your search!

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2004 X5 3.0 White on Tan/Premium/OEM DVD headrests/DICE Mediabridge
2006 Nissan Armada SE
1986 Audi Coupe GT/5 speed
1992 Jeep Wrangler 4.0/5 speed SOLD
1988 Jeep Wrangler -SOLD and gone for good
1988 Honda Hurricane 600 - STOLEN