X5 or 545i sport w/SMG Tranny

[BimmerDude]

I need to get some input from anyone that can help.
I'm thinking of selling the X5 and buy a 05 545i sport. What do you guy's think? Reason is the following:

1) Better Gas Mileage then X.
2) Upgraded car, with waaaaaaaaaayyyyyyy Less miles.

Now the down side:

1) Must go back to car payment.
2) Love my X, love it and will miss it for sure.
3) I've done all maintainance so know what I'm driving.

As you can see, I don't want to get rid of the X, but I'm coming close to the 100k mark, and warranty will be running out at 100,789 miles. I just don't want any problems to come around. So my question is, what would you guy's do if you were in my shoes? I'm kind of in between a rock and a hard place. All input would be greatly appreciated. Thanks.