Hola. You can do that with no problem. They will blend nicely,
You can use the Vanquish for center too. Because you have to aim them, you can use your walls as mirrors to reflect the sound or direct to your golden position. Bose use the reflection sound with great results...I am not saying that they are at the level of ML sound, no. But, you can get the benefit of this feature or not.
My 2 cents.
Happy listening!