tbh from what you wrote, i would stick with th S1 if its been looked after and as good as you say.

If you really want to get a 3dr, i'm sure there are ones out there that are better than the one you have written about.

IMO keep the S1, look after it and then if you want a 3dr wait til the ideal car comes along, why trade a good, tidy car for one thats gonna be a money pit potentially? The way prices are good RS's will only increase in value, where as the poor ones become cheaper.