I believe they're only available for the SR and the Miatas, but I could be wrong,
if you're looking for an upgrade, I'd suggest what a whole lot of people with higher powered cars are running, and that's the HKS ignition booster thingy

I can't remember the name, but it works with your OEM coil packs,
probably not what you wanted to hear, I'd suggest looking at takakaira.com possibly? I thought I saw some Splitfire stuffs on there,