I just purchased an iBook G3, 500/256/15/CD/OS X.4.11. It was a great deal at $100, in my opinion. I saw a 512MB PC133 SO-DIMM at OWC for $29.99. Should I purchase this upgrade, bringing my total memory to 640MB? (I would have to remove 128MB for the new one). Also, I have a Power Mac G4 Dual 533/512/160/SD/OS X.4.11. The configuration is as follows: SLOT 1 - 128 SLOT 2 - 128 SLOT 3 - 256 SLOT 4 - There is no slot 4. All I can afford is to replace a single 128 with a 512. My total would then be 896. Is it worth it?