Dave. From my maxima (frt/rear bars) and from these Hotchkis units, you definately want both. My opinion is also mirrored by our suspension guru Gsedan35 in the swaybar summary

 

I have them on medium/medium. Great mod IMO. After I got it installed in the shop, I took the freeway onramp at a brisk speed and the difference is significant. The car doesn't push like before and it's much flatter around the corner. I noticed ride becomes more jittery over bumps though.

 

Mine are on med-med. Works for me.

 

Thanks guys. I just switched from sft/med to med/med. Noticable and nice difference. Front end dives in much less now.

 

Having just a rear bar I can say that stiffer front bar is necessary for track/ autocross use. For agressive street use replacing only rear bar will be more than enough.

Stiffer front bar doesn't automatically mean more understeer. 60/40 weight distribution FWD car and almost 50/50 RWD will react differently.