What you saw launching the Orion was a Delta vehicle, not the SLS(Which has yet to fly). The SLS will not support more than two first stage boosters. The Angar

What you saw launching the Orion was a Delta vehicle, not the SLS(Which has yet to fly). The SLS will not support more than two first stage boosters. The Angara family of rockets is not meant to compete with the SLS and they're entirely different classes of rockets. The SLS could be described as a super-heavy lifter, and the Angara as a heavy lifter. The most primitive form of the SLS (without any additional boosters) is planned to be able to put 70 metric tons into low earth orbit. The most beefed-up form of the Angara is planned to be able to put only 23 metric tons into low earth orbit. Its most primitive form puts only 3.8 metric tons up there.