Or even more different...

I think this is what I would personally do.

AA1486 SFO-ORD (Lv 9:30am Ar 3:30pm)
IB6274 ORD-MAD (Lv 4:45pm Ar 7:45am)
AY892 MAD-STO (Lv 10:00a Ar 1:45pm)
SK161 STO-GOT (Lv 2:25pm Ar 3:20pm)

You get AA's 763 to Chicago, full flat beds to Madrid (unlike AY and AA), and arrive before when you're looking at with your suggestions. You also only use one NA and one Europe segment, unlike going through ZRH or FRA. You can buy the STO-GOT segment for about $50. IB gets a bad rap, but I thought they were fine and the reports of late have been much more positive (except for ground staff, which still bites).

And for what it's worth, I think christep's suggestion is good and at least worth checking out.