In my books you can afford it, life is too short - go for it.
I'd put some money down (~10K) on new one to keep payments reasonable - you dont spend a lot up front, you keep your monthly savings still in similar ballpark. It really depends on how personal view on parting with lots of savings .
Hers : 2013 335xi Imperial Blue/Black with lots of stuff...
His : 2013 X5 35d Deep Sea Blue/Black with all packages
Previous : 2010 335xi Monaco Blue/Black with just about every option...
Previous : 2008 X5 4.8i Space Gray/Black with just about every option...