For me, one of the most important issues with a mike is pickup pattern. Few take it into account, but traditional cardioid mikes are designed so the best feedback rejection comes directly from where the mike is pointing (the sharp end, that is ). However, for keyboard players, our monitors are seldom directly in front of us, the keyboard gets in the way. We put ours to the SIDE.

A super cardioid or hyper cardioid pickup pattern has rejection nodes more to the side of the capsule than directly in front, and in my experience allows you to run your vocals a bit hotter without feedback. Place your keyboard monitors off to each side, slightly ahead of the arranger, and you are in the optimal spot for a super cardioid mike...

Just a thought.