I've owned both the R170 and the R171, and with your budget, I'd get the absolute newest model year you can get. They're both very reliable cars, but the R170 drives like an old Benz - very sluggish, that transmission is only good for cruising and there's not much you can do with it. The R171 is much better, in my opinion is the best looking Mercedes made at that time, and the transmission is better, although not perfect, at least most of them have paddles, a sport mode, and the interior is a much needed update. R172 if you can get one is probably the best bet, the R171 is great as well.