IIRC, the front bar is more for show than go... according to those who race the CSVT, the front strut towers are close enough to the firewall area of the chassis that flex there is less prevalent than on other cars. The rear strut tower brace is going to have a more noticeable effect on chassis "stiffness". Stiffest way to go would be both front and rear, along with subframe braces(preferably welded in).
Hope that helps!
