One thing to consider when purchasing a refractor is how wide the imaging circle is and whether or not you will need a flattener. I'm happy with all of my three refractors even the F7 one and have never bothered with a reducer. At the same time, I was surprised 3 years ago when I mounted my AP155EDF with an APS sized chip for the first time and got oblong stars in the corners! An email (at 11PM) to AP with an example produced a return email the next day telling me that I needed a flattener. So, 650 dollars later all was well. If you stick to that ASI1600 you shouldn't really need a flattener.
If I were buying a replacement for my 10 year old TV127is, it would be an AP130GTX or even an earlier one. One of my observatory partners has one with the flattener/reducer and the raw data is just amazing using a full frame camera.
You should also, since you have time, do some research about all of the things that you will need - rings, adapters, etc. These can really add both cost and complexity to a purchase. The price tag may or may not matter but complexity is never your friend in this hobby. That becomes particularly true as the focal length gets longer and longer.