Dinan is always very expensive and typical very good. You can not go wrong. But if I were you I would look at Active AutoWerke's tune:
Active Autowerke X6 (TT 4.4) Performance Software -- Active Autowerke Online Store

Or ESS: N63 DirectFlash ECU Performance Software - ESS Tuning | BMW Tuning Parts | BMW Racing, Tuning, Aftermarket, Performance Parts | Engine Power Chips | Performance Upgrades Chip

And not to mention EuroCharged: I have their tune on my M5. Very impressive.
E70 X5

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2010 X5M /// R63 AMG...Wifey's 540HP Family Hualer

2001 X5 3.0i Sport 335,448 miles & counting...
SMG M3 Steering wheel
E46 Stainless Racing Headers
4.6is Exhaust
Turner Pulleys
Afe Intake
Brembo drilled rotors
PowerFlex Bushings
Hualingan
30mm H&R Spacers rear
20mm H&R Spacers front
Bavarian Autosport High-Performance Coils
Active Autowerke's Performance Software