In my opinion, the sport seats are a MUST on the Cayenne Turbo. But if your "rear" is a bit wider than avarage, you won't be happy with them.
Otherwise, they provide great sidegrip and are a great option to have.
Other must have options? The advanced off-road package is an interesting option, even for street driving but it costs a lot of money and I'm somehow worried about the swaybars.
One reason why I didn't go for this option. But if you're doing a lot of off-roading, the advanced off-road package might be a must have option too. Also get the off-road navigation.
The front protection plate is another nice thing to have.
I also like the insulated glass on my Turbo, it provides the same dark privacy glass in the rear and when the sun shines, the heat in the car builds up very slowly. If you have kids or if you're a lot in hot areas, the insulated glass is a great option to have. It also provides a better theft protection, it is pretty difficult for somebody to brake the glass, he would need some serious hammer and a lot of force to penetrate it and this makes a lot of noise.
Somehow also a help against car napping.
I also like the sunroof but it is no must have option.
Also get the CD changer. I got the 20'' Sport Techno wheels on my Cayenne Turbo and I just love them. They look nice (much nicer than I thought) and the low profile tires provide great fun on the street. However, today I did (or tried) some "off-roading" (I had to turn my car and drove over little bump of tight earth) and I failed miserably. The tires had serious difficulties to keep up with traction, it sounded horrible and I can't recommend the 20'' street tires for even the easiest off-road tracks.
Clever Turbo owners who like doing off-roading too, go for two wheel sets: 18'' wheels with off-road tires for off-roading and 19'' or 20'' wheels for street driving.
I'll post a picture with the sport seats later on.
) and I don't know when I get home today. 
