✔ 最佳答案
I don't stay in Hong Kong often so I don't follow the used car market price, but I would like to pitch in my recommendations.
Audi: You will probably go for the B5 generation A4 1.8T (between year 1997 and 2001). You should get the one with quattro AWD because it's a lot more fun to drive and I still don't know why people by Audi without quattro. The B5 generation A4 has better built quality than the B6 A4 (2002~around 2006). Don't touch the V6 models as they are heavy, very poor low-end torque for start up, and gasoline gulping. Check the service record on the 1.8T, get a car with consistent engine oil change record. The turbo and the engine are both very reliable as long as engine oil are changed every 5000 km. The only issue with the car is there's a major recall for first batch of turbo wastegate which lose control on the turbo pressure; and in later years there's a recall for the ignition coil pack. However, I am sure as long as the car you test drive drives ok, those two issues should have been taken care of as the problem can be easily detected while driving. I know a lot about this car because my wife used to have a B5 A4 and my brother still is driving a B6 Avant (station wagon in Audi's term). The B5 is a great handling car with quattro.
BMW: As another user pointed out, the E46 (around 1999~2005) 318i is a pretty good deal, and also is newer. I think for the price you may be able to get a E46 320i as well. E36 (1991~1998) 325 and 328i are quite solid car, fun and great power/handling balance; but for this generation at this age these BMWs are infamous for leaking sun/moon roof. Again, my wife replaced her A4 with a E46 330xi and my cousins and friends have the E36 325i and M3, so I get to know quite a bit about those two generations of BMW 3-series, too.
Mercedes Benz: Another bro has mentioned several options already, so I am not going to repeat here. Just don't get the 1996 and 1997 E420 as the transmission has problems. You probably should avoid S-Class as well because the maintenance cost is pretty high.
In Hong Kong, it's probably easier to get skillful technicians to fix a BMW and MB because there are plenty of them compared to Audi. I won't call BMW and MB "rubbish", as they are still making good profit (BMW just posted record profit last year), and I don't think you can make profit by selling "rubbish" products to the world market.
You should also consider saving money to get the shocks and springs replaced depends on the year of the car you are going to get because for the road condition in HK the shocks may lost most of its rebound capability after 90,000 km.
May I also suggest that you should take a look at Lexus IS/ES and also Acura TL. Those are very good car, very reliable, less likely to break down, and cheap to maintain and fix.
Hope it helps and Good Luck!