I would just stick with the suspension with the way it rides stock. Add some winter tires and you can honestly crawl through just about anything. Good friend of mine in Denver uses his X5 for only winter weather. Takes it places on the weekend that would scare me. Just be aware of your clearance and you'll be fine.

I personally don't use my X for this, this is when a FJ comes in handy......You can also keep your current stuff and look for a used FJ80. There are plenty out there plus there is a Indi shop just north of Denver that is the bomb.

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2001 4.4i Alpine White-Bone Stock
2001 Discovery II SE7 Black (A money pit)
1996 FJZ-80 Black (with some goodies)
1969 Firebird (work in progress)