Not saying your buddy doesn't know what he's talking about, but all cars are different. A uni-body contour is quite different from the cars he's used to.
All cars have chassis flex. And yes it's good to improve it. But a front strut tower bar is not even close to being the most effective (if at all effective) suspension part for contours. Subframe connectors would be better than the fstb. But as far as doing either over good springs and struts, I wouldn't go that far at all. Good springs and struts will make the biggest difference, then a bigger rear sway, rear strut tower bar, and so on. But don't forget, the most important thing is tires.
-------------------- 98.5 SVT
91 Escort GT (almost sold)
96 ATX Zetec (i brake to watch you swerve)