It's hard to quote a price if you don't specify how you would spec the car, but at full MSRP with the Exec Package and the 20' wheels, your payment would be around $1,690. Subtract about $30 for every $1k you can negotiate off of MSRP. This will get you in the ballpark +/- a few bucks.
Ordered: 2016 Silverstone F10 M5
Current: 2013 Monte Carlo Blue F10 M5 (ED on 9/1/12), 2014 Anvil WW Jeep Wrangler
Previous: 2009 Carbon Black M5, 2006 Silverstone M5, 2003 Sterling Grey M5, 2000 Anthracite 540i6, 1998 Jeep Grand Cherokee 5.9Ltd, 1990 Eagle Talon TSi AWD, 1978 Mazda RX-7