Please ignore (or Admins, delete) this post. It would seem that I am very unaware of the value and ability to expand the G4 Cube.
I will take the advice of a poster (thank you very much for opening my eyes) to sell the G4 PowerMac, then use that money to purchase a Cube on eBay or this Marketplace.
I hope that I've not insulted any Cube owners (or PowerMac owners). If so, I apologize.