I found that upgraded springs and dampers (Lovell & Boge/Sachs in my case) noticeably reduced roll and tightened handling without seriously degrading ride on 215/60R16 tyres. I ended up deciding that I wouldn't try upgrading the rear swaybar as I didn't think there was going to be enough benefit to offset the risk of getting caught by unanticipated oversteer in treacherous conditions, especially as the upgraded springs did reduce the tendency to understeer anyway.

Even though I've gone through 225/50R17 (98 load rated) to 225/45R18 (which is at my limit for ride quality), I sometimes think I should go back to 225/55R16 on 16x7 wheels for most of the driving I do with the suspension setup I have.