if your not thinking of track days id probably steer clear of coilovers, instead id go for eibach/h&r lowering springs matched to KONI FSDs as that setup is very good for road use, and IMO opinion better ride than standard in all departments. Damping is just as important to handling as spring stiffness.
on ARBs
Rear wheel drive cars- increase the front bar to reduce understeer, and increase the rear bar will increase understeer
front wheel drive cars- are the opposite. Increase the rear bar and reduce understeer, increase the front you will increase understeer, however if you increase both and overall roll and understeer will be reduced whilst keeping the balance of the car neutral. to stiff on the rear and you'll be pushing your car to understeer a litle more when pushed. I have the eibachs front and rear with the front on the softest setting and rear on the stiffest setting and IMO opinion it is very good. (I am considering a bigger rear bar again though but i am very track biased)
Also if you are considering WALk, and you also go for Front and rear ARBs, get them fitted at the same time to save paying for two lots of geometry work, as the front ARB and WALK both require this.
Agree with the guys also about the 19" wheels. you will start to cancel out any handling improvements with massive wheels. 18s are fine, even better if they are lightweight
