This site is excellent and you will get some of the best deals.
If you want a bit more of a dealer experience, Vin's Motors is great.
Read More . 1 year warranty on any car and free pickup/dropoff for service as long as you own the car.
I have heard, but am not sure it is true, that rollback is not explicitly illegal in HK. On the other hand, most cars don't get a huge amount of use compared to their foreign brethren, so older cars tend to be in rather good shape comparatively.