I think it's a SMART MOVE if you want the car!!! Ask Bob aka Standby about depreciation. The depreciation on a relatively new one --2006 is about $30k in a little over 14 months.
If you GM SMART LEASE IT you can pay up fornt and save the interest carrying costs. ALso they will calculate the "residual value for you at the the end of the lease with you can then elect to buy.
My guess is that a 3 year old XLR-V (2006) may be worth about $45k with low mileage --36k IF it is Cadillac Certified.