I've used hired cars to go from both SVO and DME to hotels in the city center, but I generally find that they're not worth your while. Traffic in Moscow is absolutely horrendous, and unless you don't mind being stuck in a jam for a few hours (doesn't happen to me every time, but often), I would highly recommend Aeroexpress. Fast, clean, dependable, relatively cheap, and English-speaking. You could even have a car pick you up at the train station and take you to your hotel and still come out ahead, in terms of money and time saved.