Anything over 1.2ghz is interesting. Wanted to look here before I start paying insane ebay prices for one
Knezzen,
I was almost going to post the same message as Garry, glad I didn't, lol; since I thought it was a snowballs chance in hell of finding any "cheap" cube upgrades. I think that is what Gary meant buy "are you kidding"... surely we know you are serious about wanting to upgrade it and nobody here thinks by any means you are stupid.
The Cube unfortunately (since it's like the Holly Grail of the silent DAW search) is definitely NOT a cheap CPU upgrade, and there are not many out there. The quietest Cubes (with no fans) peak out, as I am sure you know, at 500MHz (standard Sawtooth CPU with 100 bus). Another approach is to find a G4 Sawtooth upgrade that should work in a Cube as long as you can fit the Fan/Heatsink or find a retrofit method.
I remember it like yesterday, as a vendor at "MacWorld" in New York in 2000, I was helping out at the Steinberg Booth and Apple was pushing the Cube at full throttle. It was the main theme at MacWorld 2000 with Cube demo units everywhere and 20 foot posters all over the place. They gave us about 4 to demo with Audio Apps and at the time I was very impressed at this silent little machine. My love for Cubes went on for about 5 years and I applied almost every know mod/upgrade. I eventually gave up on my beloved cubes since they lacked the internal PCI slots I needed for the PowerCores and UAD-1 cards. It is still such a cool little unit. For a while on eBay, I was buying old cubes to chop up and sell as parts (since the individual parts brought 2X the money as a whole unit) back around 2005.
Now with SSDs available, I wish i still had one; they still ran well with CuBase 4.1