The 320 is a 6 cylinder 2.2 (2171 CC) IF it is the a certain year or newer I believe?

If I was going to buy a BMW it would have to be 6 cylinder or more, a 4 cylinder is just not right (Like the horrible supercharged Mercedes engines) (Plus the E46 318 and the like are known for blowing HG'S)

318, as you say is 1.9.

Most of the 6's have been dropped in later models, for example, the E90 320 is 4 cylinder and is actually a 2L I think, while the latest 3 series, the 328 is actually a 2L four pot twin turbo , it's done for emissions reasons mainly, the same as Ford have dropped the lovely 5 pot Volvo engine!

Martin