I would say that most guys who've had these cars for awhile end up bypassing the ARC, and going with Konis or Bilsteins. I had originally put the Tokico Illumina 2s in mine with the Eibachs about 3 years ago, but after about 90,000 km (approx. 55,000 miles) the rear shocks were pretty dead, and the fronts are on the way. I've put a pair of Konis just in the rear for now, and will do the fronts over the winter. Originally I wanted to be able to retain the soft / firm feature, but usually I'd be driving with the firm setting on about 95% of the time anyway.
So the short version is, yes, if you like good handling out of the SC, step up now for some Konis or Bilsteins, then your done with it, no messing around later. If I had known better before I just would have gone Koni originally. I was afraid they would ride too stiffly, but I should have remembered how they were in my 87 5.0 Mustang -- fantastic in that car too.
cheers
Ed N.