If someone makes a hollow sway bar that is an 'upgrade' over OEM, i'd highly reccomend it. Even with the increased roll stifness of coilovers, wheel deflection will be greatly reduced, which means the amount a swaybar contributes to roll stiffness is decreased. Hotchkiss makes good products on all platforms i've had the pleasure of driving them on. At least on my application, they are very large, but hollow. Lighter than OEM swaybars and on the lowest setting provide a solid increment of greater stiffness. At the highest setting, they rival the stiffest swaybars made for my application. I'll be honest, the difference between having my front sway connected and disconnected (on lowest setting) doesn't increase front grip at all. But it is more responsive with it connected. I also run very stiff springs and wheel deflection is small. Having an OEM bar wouldn't benefit me at all as it wouldn't increase grip, it would have slower response, and it would be heavier. My hotchkiss is 32mm hollow and the OEM bars were 24mm solid.
Lots of good application specific advise here, just thought i'd highlight the reduced wheel deflection and swaybar contribution by having stiffer springs :)