You can afford a lot of repairs for that price difference. One car is a limited production future collector and the other is a standard luxury sedan that will half its value in the next couple of years. Some say get the newest "insert car manufacturer name here" you can afford, I say get the one that excites you the most and makes the most sense for you. Personally, I think the RS6 is the better value here. S6 may provide you with more reliability, at a cost. You get to decide how to spend your money so enjoy the process and let us know what you end up getting.