My opinion would be to sell the 320i and take full advantage of the abundance of 330i Auto's available, go test drive a few. It is light years ahead of your 320i in every way, brakes, suspension, drivetrain, torque!!!
Fuel economy is awesome on the 330i if driven nicely, my gf's 330i 5spd manual averages 8.8lt/100km when she drives it, when I drive it its around 9.6lt/100km but on the open road I got it down to 7.8lt/100km @ +-128km/h. The good fuel numbers is because of the 300nm of torque, you don't have to floor it or rev past 2.5-3k to get going quickly and still get 650km per tank.