My 2003 ztw wagon came with a rear sway bar. Check to see if your 2006 did. If not, it will help. Strut braces are almost useless on our cars, but the sways will help.
Also, I did eibach springs and shocks . lowered the car about an inch or so. All the stock focus parts fit in the front, but the rear shocks are unique to the wagon, as said above.
Speed is only a matter of money; how fast do you want to go?