Bahnstormer, I think you are right, you're sending the shock to both sides, but you're also splitting the impact a bit. Instead of one wheel/spring/strut taking all the impact, the stiffer sway bar absorbs some of the impact and transfers it to the other side. IMHO it is a great mod and should not severely affect the ride quality.

Gale, she's got the stock wheels and tire sizes. I'm sure you're right, much of the roll is sidewall, but I'm not going to spend more on a new set of wheels for her. I think the sway bar upgrade will help enough for me to enjoy her car, yet retain some of the original ride quality so that she does not complain about how hard the ride is (as she does in my 535).

And yes, I'm about to call BMA and get the M5 sways, kewl, and thanks for all your help guys.