Any decent motorised Dob will be fine for planetary imaging with a video, and a 16" is easy to manage singlehanded. The difference for visual observation between an 8 and a 10 is relatively minor in practice. The jump to a 16 is a much more natural step up for visual work. Even a well designed 18" can be moved around in a small car, and most of them don't need you to be climbing ladders to reach the eyepiece. Visually, aperture rules.
The main reason a 10" SCT EQ would be an upgrade from an 8" dob is if astrophotography is going to be a big part of your hobby, which it sounds like it will be. Also, as others have said, if you're planning on using the full focal length of an SCT, the mount is going to be the limiting factor for your imaging. Then the fun starts - better camera, filters, then a bigger scope, then a bigger mount, then a new camera will emerge so you can justify a bigger scope, which will need a field flattener and a bigger mount, so it's worth buying the newest gen camera with a guide chip inside...etc... until your family desert you and you come to your senses living inside the shipping carton your RCOS25" arrived in...
cheers,
Andrew.