A 650 has little advantage over the 550 if it doesn't have the case feeder in the speed dept. It's big advantage is being able to handle all those longer cased calibers. Were I you? If I had the room, I'd keep the 550 and add the 650 to the bench.
On my bench, I run a rock chucker on one end, and a 650 on the other. And quite frankly, I would HATE going back to just one press after having 2 available. I've just found it to be highly convenient.