Welcome and congrats on the new X3. Personally I would be ok with the '05 loaded pkg. I have an '04 2.5 and have a friend that just bought an '05 3.0 and there's a hefty engine diff. Others have posted to the board regarding the '06 features. Even so, the 3.0 engine in there is a proven entity and is plenty (in my opinion) to help the X3 scoot. It also sounds as though you're getting a sweet deal on the rig to boot. Now is as good a time as any to make the move. My local dealers don't discount "old" models as they know it will sell regardless. Still, the lease deals are pretty sweet right now. I can actually get a loaded 3.0 for less than my moderately packaged 2.5. Also, with a lease being all about depreciation, you may find the '05's loose some of their low lease payment with the introduction of the '06 (that's how it was with my '05 325i lease anyway).

As for the all seasons, it depends on your weather. I've got the all seasons in wet weather (I have yet to experience them in snow) and have had good luck so far.

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MWBBMW
2006 X3 3.0i Highland Green Metallic, Sand Beige Montana Leather, Steptronic, Premium Pkg, Cold Weather Package, Privacy Glass, Xenon Headlights
2007 328i 6-speed, Black Sapphire Metallic, Sport package, Black Leatherette, Heated Seats, iPod & USB Adapter
If God had intended man to walk or fly, he would not have made BMWs!