I just put a set of Suspention Techniques sway bars on three weeks ago. So far I am very pleased. Purchased them from http://www.turnermotorsports.com
$309.00 for the set. 22mm front and 19mm rear. You have to strenghten the rear mounting points on the trailing arms. they give you some plates for this in the kit. I took mine a step further and welded the plates on and added angle supports. I think this set is the largest/stiffest that is avaliable. I have to say that i have no rearend slop and the roll is less than my wifes 03' 325i.