It kills me too when I see ATA133 cards for PC's for so cheap. Unfortunatly you must buy a Mac card though. I have both an Acard based ATA/133 RAID card, and a Sonnet ATA/133 standard card. (The Sonnet card has a "Promise" based chipset)
Both work great in my G4 Quicksilver DP800. Both offer big drive support as well. I'm running 10.2.8 & 9.2.2