You'll get dark enough, alright. CMC's roasted grains DEFINITELY darken the wort. I'd actually recommend halving your amounts, and DEFINITELY leave out the molasses. The D-180 (or is it D-90? No such thing as D-190...) will help things out, too. I can tell you that in a 3-gallon all-grain brew, 1 lb of their dark-roasted buckwheat got me well into porter territory as far as color goes. Can't comment on the flavor yet, but definitely a HELLUVA LOT darker than anything I ever home-roasted. Leave out the unmalted buckwheat, too. You should be fine just steeping the malts, they won't have any diastatic power of their own and you won't get much sugar out of them even with enzymes.