your best bet is to flash to a custom ROM (I use MightyROM, but there are many out there) using
http://forum.ppcgeeks.com/showthread.php?t=42503 to unlock it and then any ROM of your choice.
Before you flash, in the folder containing RUU_signed.nbh you will see a program called PagePool Changer. Launch that, and change the Page Pool to 12. You will have a lot more memory just doing that.