I have a magnum 61 in mine, fits in the cowl and it flies nice. The magnum 91 is the same external size and is on sale for 119.99$ at hobby people. I would get the Mag .91. I'm not sure about the tower but it is about the same size as the Magnum.
I recently picked up a SK .80 from kangke for 70$ and i'll probably replace the Mag .61 with the SK .80(alot more power).