Update: This article was originally posted at 6:30 AM and updated at 11:00 AM with a Spin.

Several months afer the expected announcement, Apple has announced that ATIis new Radeon graphics card is immediately available as a build-to-order option at the Apple Store. Original speculation had the Radeon replacing the Rage 128 across the line, but the Rage 128 will remain the default card in the G4 and G4 Cube. According to Apple:

Apple® today announced it is offering the Radeon graphics accelerator card as a build-to-order option on The Apple Store™ for all Power Mac™ G4 and Power Mac G4 Cube systems. Priced at an additional $100, the Radeon graphics card provides the most advanced 3D graphics processing available for the Macintosh®.

“Apple’s new line of dual-processor Power Mac G4s and the all-new Power Mac G4 Cube provide creative professionals supercomputing performance and stunning design on the desktop,” said Phil Schiller, Apple’s vice president of Worldwide Product Marketing. “The combination of the PowerPC G4 with Velocity Engine and the Radeon graphics card make both the G4 and G4 Cube incredible solutions for graphics applications and 3D games.”

Apple in July introduced the new dual-processor Power Mac G4 and all-new Power Mac G4 Cube, both of which feature the PowerPC G4 with Velocity Engine™, delivering supercomputing performance on the desktop. The new G4 is the first mainstream personal computer to come standard with dual processors. The Power Mac G4 Cube is an entirely new class of computer that delivers the performance of a Power Mac G4 in an eight-inch cube suspended in a stunning crystal-clear enclosure.

To perfectly complement the new G4 and G4 Cube, Apple also unveiled a completely new family of displays. The new displays include: the 17-inch (16-inch viewable) Apple Studio Display CRT; the 15-inch Apple Studio Display flat panel and the 22-inch Apple Cinema Display, the largest all-digital flat panel ever brought to market.

The Radeon is available as a BTO option for US$100. You can find more information at the Apple web site.