Going for a 19" alloy over an equivalent 18" alloy will in most cases make the handling worse and accelleration times and fuel consumption worse too. by going from my oem Talladegas to aftermarket lightweight alloys i removed 5kg a corner from the car and as that is off unsprung rotating mass the benefits on accelleration are four times the weight saving - equivalent of removing 80kg from the car!! I preserved the 235 section width of the tyre, so no loss in traction either.
My advice on coil overs would always be the same.......Bilsteins.
If you can afford them Bilstein B16 PSS10's are excellent. If not B14's offer the same drop, but not the damping adjustability.
As long as you don't go silly low the suspension is very OEM like at setting 1 but like a race car on setting 10.
Mine just after the drop. There is about another 3/4" (19mm) left to go down on the coil overs too!