I bought an ICEfx Ultra (x8 100Mhz processors onboard) for my Media100i 7.5 running in OS9, via ebay.
The great thing about it was the plugins….they work in Adobe After Effects, but also Boris FX. So the main advantage for me was that instead of having to export to After Effects all the time, to use any decent plugins, I now had much better plugin options from Boris FX – as integrated into Media100i. So instead of exporting, I could just double click a Composition Clip in the timeline, click Edit, it would open Boris FX, I could apply my effect, exit Boris, returning to Media100, and then click “Render” to render the clip.
IceFX promises significant speed increases, but doesn’t deliver these. The IceFX I bought via Ebay came with Final Effects Complete plugins also, which I believe you can also buy as standalone software. You may be better off doing this, as 800Mhz of processing power on a card, doesn’t really make much of a difference when you’re running a 450Mhz Dual Processor G4 Mac, as I was. I had therefore 900Mhz of CPU power…and you just don’t notice the difference between that an an 800Mhz specialist card.
In short, ICEFX Ultra and Final Effect Complete, gives you some nice plugins that you can use in After Effects or Boris FX, but the hardware acceleration is insignificant compared to the power of today’s Macs.