Yep, I'd also go with the filet, and agree it shouldn't need sauce. If you feel uncomfortable asking for it without sauce, I'd maybe count the steak calories and add maybe 50-100 calories for the sauce. You should be able to type 8 oz filet into anyone of the calorie sites and get an idea for how much it is. Steak is great protein, so you really can't lose there - unless you don't like steak.
Besides, steak prices are going to skyrocket pretty quick here so might as well have some now.
It might be worthwhile asking if they have an alternative vegetable like broccoli instead of potatoes.