I have Z4 with adjustable Koni's. They're great for that 3,000 pound car.
The Speedster has KYB Excel-G (gas) all the way around. The ride is firm, ...um hard. We have a crew installing bumps and pot holes here...don't know what they're paid. I've been looking for a softer shock for the front that would still provide good handling and really haven't found much. Oil shocks seem to, almost be, a thing of the past. There has been some discussion about EMPI shocks but I just can't pull the trigger on those.
I would think the Koni's would be too stiff even at the low setting. That's where I have the Z4 shocks set.
What to buy?
I've got them and like them, and you have at least 3 other positive testimonials on this one thread.
Do what you wish, but the combination of EMPI sway bars, Koni shocks, and Vredestein Sportrac 5 tires is an almost perfect balance of comfort and handling in an IRS speedster. You'll hear folks advocating for light oil shocks, which are probably fine for cruising. I've got zero complaints with my setup, other than those engendered by having a beam instead of an A-arm suspension.