Don't bother with anything other than the Scorpion STRs, or maybe the P-Zero Neros (assuming you're looking for all season tires -)

Use the 'Search' function, this has been discussed alot. The Scorps are far and away the most synergistic choice for the X3. I've got them on my '04, been thru a couple good winters here in Santa Fe, they've been simply excellent- very good day-to-day, great handling, good ride, quiet, very good in wet, very good in snow, wearing well (I've got 40K on mine, will replace next fall). The car likes these tires, & vice versa.