Are you doing the work yourself? or are you going to a shop?
Ive had good success with parts from FCPEuro, or ECStuning,
I redid my front suspension (regular springs not air) and the bill was reasonable! changed all the front pieces, (pressed in a new bushing into the tension struts) and also changed wheel bearings. Used mostly Meyle HD parts and FAG bearings.

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2003 X5 3.0i (02/2003) sport package, Sapphire black metallic / Black Dakota Sport seats. compass mirror retrofit, trailer hitch retrofit, Prodigy P2 trailer brake controller installed, PDC retrofit, Lumbar support retrofit. heated rear seats retrofitted. Running boards retrofitted and subwoofer install in progress. 4.8is Brakes installed front and back. Bluetooth TCU installed, Rear Fog lights installed. Retrofitted reclining rear seat backs.