Galaxies require dark skies and lots of aperture. A Dob would be a good choice if you hadn't mentioned planets. Planets are small, and you'll want more magnification. (As noted, they will still be frustratingly small.) -That kind of rules out a Dob.
Tony commented on this, I also think it needs a comment.
The planets are small, Jupiter is about 40 arc-seconds across, so to see the details, magnifications of 150x or more are desirable, generally somewhere between 150x and 250x possible. This is primarily determined by the stability of the atmosphere, the "seeing."
The amount of detail that can be seen also depends on the quality and size of the telescope. Larger apertures provide better resolution and better planetary contrast. In general, this favors a scope in the 8-12 inch range. A 10 inch Newtonian can provide more detailed and better resolved planetary views than even the best 4 inch scope.
The only issue I can see that might be of concern is the need to manually track most Dobsonians. I don't consider this an issue, it does take a short while to learn to manually track a Dobsonian but what I find is that people seem to learn it quickly, tracking at 200x without much difficulty within a few minutes. To feel confident, it takes longer but it's not difficult for most.
When I want the best planetary viewing, when I want to split the tightest double stars, I almost always choose a Dobsonian. Granted I am skilled at tracking by hand but planetary views are at relatively low magnifications compared to what is possible..