Is the X5 4.8is right for me...

[Secure]

My requirements are...

Quick/Torquey/Can hustle a bit [no problem]
Decent sound system [subjective, great IMO]
Can carry a couple surfboards (shortboards) with or without a roof rack [no problem]
Automatic (duh)
Light off road/camping capability [very light]

By light off road capability I mean dirt trails with small ruts or driving on the beach. I go camping/on trips a lot. Most of the places I go my friends Civics and Camrys can go, but they get stuck/have trouble. So its not like crazy "real" off road stuff.

My friend also told me to look at a Range Rover Sport Supercharged, but this car seems really large and I've heard many stories about Land Rover reliability issues. Porsche Cayenne also came into the picture, but I do not know much about Porsche in general. [no experience]

I'm also leaning to BMW because I've owned two that were pretty reliable, and have a fantastic shop (Avus Autosport in Glendale, CA). [compared to what? Every BMW I've owned required frequent unscheduled maintenance. best driving car ever if everything is working]

My main questions are

Is the 4.8is quick enough to be somewhat similar to my current Audi in terms of passing Prius drivers etc? [without breathing hard]

Is it fairly reliable compared to the other brands (Range Rover/Porsche etc)? [probably equal to other German brands]

What is the deal with the adjustable suspension? If it is set low for city driving does it stay low? or is it a vehicle entry/exit type feature? [My understanding is that low is for easy exit/entry, normal is for all driving, high is for "off-road driving"...all manually controlled with a switch on the dash]