For road use I would recommend KoniFSD but for track I'd be looking at the Bilstein coil-overs and modding the whole suspension.
As you write:
"My priority is to improve handling and road holding and not to sacrifice comfort; improve comfort would be a bonus", then the FSD system would be difficult to beat in my opinion.
RR's KoniFSD+Eibach Thread
How KoniFSD's Work
To get the most out of a suspension mod I'd also be considering Anti-roll bars and springs, but it's extra money and a slippery slope [img]/ubbthreads/images/graemlins/grin.gif[/img].
Hope this helps [img]/ubbthreads/images/graemlins/169144-ok.gif[/img]