Our car is fwd so it suffers from understeer. I would go with just a rear. If you upgrade the front i would just do what i did and get the stock front sway from an 03. It brought back some of the understeer but it is definately better driveability overall.
the problem with the front strut bar is that the kit (eibach is the only one who makes a front) keeps the same difference between the front and rear bars. The tib suffers from understeer, like said above. When you put on a stiffer rear is gets rid of alot of that understeer. Now when you add the Eibach front to the car the differance in thickness on the font is brought back to the same point relative to the rear....so the same mm differnce in thickness....this means that while bodyroll both front and rear is drastically reduced the understeer of the car is only slightly so.....
I had the eibach kit on for a while with my quest coilovers.
I would up with some massive understeer unless i cranked up the preload in the rear for the quest coilovers....then the ride was soo harsh it was nearly unbearable.
since then i've gone back to the stock front swaybar.
as far as i can tell tho the eibach rear is just the ticket. Seems to be doing its job nicely.