I got some Yokohama's yk520's i believe at discount tire, good reviews, much quieter than the dunlop sport 5000 i replaced. These Yoko's come in various sizes, i have 03 x5 4.4i on 18" as well.

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2003 BMW E53 X5 4.4i - M62 engine (Non Sport with Premium and Cold Weather Package)
Color: Steel Gray Metallic
Mods:4.6is Exhaust (Pipes, Mufflers and chrome oval tips) BMW Sport package Taillamps, BMW Tire Valve Stem Caps
Medium tinted front windows
JVC HD Radio
Alpine 4x100 channel Amp
Orion 600W Mono HC Amp
Three 12" Sony Xplode in subwoofer enclosure