I find my stock xkr coupe 2002 rolls too much for my liking in tight curves where speeds of 50-60 mph are easily achieved.
My car is fully maintained with replaced bushings and front shocks in the past 18 months so this is a question about improving the car beyond stock.

Were there any improvements done in the final 2006 models that could be applied to my 2002?

the larger rear anti roll bar from UltraRacing looks promising but I suspect the lower chassis braces for front and rear would not do much for a coupe.

Oft touted PowerFlex purple poly bushings going to help?

Lowering springs make a difference for this?

 

I like the powerflex bushings but doubt they would do much for roll. The anti roll bar should help and then it's changes to the dampers and springs.

There was an R performance pack that has different anti roll bars and different shock part numbers listed. It is a CATS setup, though, so the shocks are $500 per and if you don't have the active suspension on your car then you would need the controller, wiring and all that.

There is an adjustable coil over kit from Spires in the UK. It is built on standard Eibach springs, so you can choose any spring rate, they are height adjustable and they offer different damping rate options. It also comes in CATS and non CATS form.

It's pricey, but I've started looking into it since the stock adaptive suspension is so expensive. For the cost of 4 new adaptive shocks and a set of mina lowering springs, you get within $500 of the Spires kit.