I am wholly unqualified to offer any comparative preference for one mount to another, because I have only one and only for the last 2 months. Also being a Nikon daylight shooter for years, I added a tracking mount to my equipment pile just like you're considering. Right now, my heaviest camera/lens combo is just shy of 10 lbs, add some wires, a heater, dew cover, and a few other accessories and I am sure to be pushing 15lbs. So I wanted to at least start with something rated for 15-20#. That brought me to the Orion Skyview Pro. I found a deal on ebay for one with the tracking motor kit and a polar alignment scope installed for just over $250. I see one up there right now cheap:) For Reference, had I bought it from amazon, it's $565. That will hold my equipment without issue, and the included tripod is a beefier then my Manfrotto, and probably yours. And the mount it's self, for the price, is very heavy duty. I was pleased once I saw it, I didn't want something flimsy that I would be worried would break under the weight of my camera.
Again considering my 2 months of astrophotography experience, I like my mount. I have all the confidence in it's ability to support all of my setups, and it has tracked well for me in the half dozen shots I've taken so far. There are better options, and I figured I would get started on the cheap and if it keeps my interest I can add more to it in the future.
One drawback of MY setup is adding the GOTO hardware is another 400+ bucks, because the motors are different. But in my target choices so far, I am not missing it, yet. If you think you will want goto capability and guiding, in a plug and play solution, then going for the goto kit from the start would be the best.
Another consideration is portability. I shoot in my yard, but if you will be traveling a lot, the mount w/tripod is 40lbs w/o the camera. But it can be easily broken down into some small manageable pieces.
I am interested in seeing how Andromeda(M31) comes out with your 200-500!