I am about to begin mixing my project in DP 4.5. I run OSX on a PowerMac G4 dual processors that rate at 867 mhz each. My memory currently stands at 768 MB

Guesstimating I have about 32 tracks running simultaneously during playback. This does not include any plugins. I will be using a UAD-1 while mixing. Is it realistic to think that I'll be able to mix using plugins on all these tracks, real time, during playback?
How much memory is enough?

All feedback is appreciated.
Joshua