Congrats. Brakes on BMW's are very easy and saves a ton of money.

I usually get the kit from brakeoverstock.com for ~$320 that includes front + rear rotors, pads, and sensors. They are a super cheap rotor but I've used them on 10+ vehicles and while not as good as Zimmerman, Brembo, etc... I've also never had an issue with safety, noise, short life, etc in daily driving situations.

Brakeoverstock - Products - 2006 BMW X5 4.8iS

I'm sure some here would advise against this "brand" (Callahan) as they are really inexpensive... but as I said... I've never had an issue.

__________________
2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)