The simple answer is no, the RS4 isn't worth double an S4. But that's not the whole story. If you are looking for value for money then keep the S4 but if you really want an RS4 then pay the going rate, its just down to that.
In UK every manufacturer fits summer tyres to their cars from new. A summer tyre is the best tyre to use providing air temp is over 7c which in the UK is most of the year. Winter tyres are better for the few weeks when temps drop below 7c. All season tyres are a compromise, not as good as a...
Road noise is largely dependant on wheel size and tyre manufacturer/model. In general the smaller the wheel diameter the greater the tyre wall height and hence the quieter the tyre. What tyres do you have on the A4?
No, I normally drive in auto and change to dynamic when I want to make more rapid progress. I manually switch off the auto stop/start, in fact it's never turned on as I have it setup to remember the last setting it was in.
May not be caused by accidental pressing of the key, i had a Mercedes ML where the tailgate occasionally would be open in the morning despite being closed when i retired for the night, i would check. Ended up being an issue will the car electronics but i can't remember what it was exactly.
I often find myself looking at the Mercedes AMG cars to replace my S5 but I do still love the shape of the sportback. Maybe a 3rd car will be in my garage before too long, I own a Mercedes SL500 as well.