i recently back to back tested stocko's vs splitfires, stockso were f**k knows how many genuine km's old out of an r32gtr engine package, punishing both sets of coils on the dyno stock where better, not buy all that much but considering the condition of the stocko's and the splitfires(barely10-15000km's old) i'll never use anything but stock coils again.
splitfires are good on a budget replacement, but dont expect as much out of them as you'll get out of standards
and yes that HKS ignition amplifire is about the only upgrade out there that works successfully for these things