First off, great financial responsibility! I wish more folks would follow this, and as a result, can weather the storm in the economy a little better. You can adjust your 401K contributions should you need more cash upfront. And you guys don't meet the dreaded AMT so you're safe on income taxes. Because of the take home amount, I'm guessing you either have a low mortgage (you're in Phoenix after all and housing prices a tad better than out here in the Bay Area) or you're renting a really swanky place.
Either way, since you're young, you might as well enjoy it and it's well within your affordability range. I'd look at a 2012 with all the dealer and factory incentives being piled on top of it. A fully loaded X5d can run around $55K after discounts/rebates from what I've been reading recently. $10-$15K down and you'll be pretty comfortable making the monthly payments.