I just picked up an Apple Power Mac Cube. Ever since it was released in 2000, I've always wanted one of these, but up until recently they were quite expensive (even though it was discontinued in 2001). In fact, one of the main reasons it failed so quickly was because of its high cost. However, despite being almost 5 years old, it still remains the most beautiful computer ever created, and I'm very happy to have one in my possession.
With 1 GB of RAM and a 7200 rpm 120 GB hard drive, this G4 450 Cube does suprisingly well in OS X. Still, a G4 450 can only do so much. Faster CPUs are desirable. Fortunately with the right hardware, Freescale's G4s can be installed in older machines, including the Cube.
Immediately after I picked up my Cube, both Sonnet and Giga Designs announced new 1.7 GHz G4 7447A G4 upgrades for the Cube and other G4 Power Macs. Giga Designs is also offering dual 1.7 GHz Power Mac upgrades, albeit not for the Cube.
Rumours also have it that announcements from PowerLogix are imminent. Expected are dual Cube 1.2-1.4 GHz G4 upgrades with custom voltage regulators, in the range of US$599. Other G4 upgrade products are also expected.