Yes, I would go straight to the 750.
I had a 650 years ago, got out of the game for a while, sold my press and gear. I then got back into it and bought a 550 and wish I would have went with a 650/750.
Don't get me wrong, the 550 is a great press especially if you are going to be loading several different calibers including rifle but the 650/750 is a nice step up with the auto index and shell feeder.