Hum.
Parece que não está disponível para o Saucy.
De qualquer forma, pode ficar com o opensource, está funcionando muito bem aqui, no Unity só se for em 2D, mas no caso do Xubuntu, Lubuntu e Linux Mint funciona de boa.
Veja:
*-display
description: VGA compatible controller
product: RV710 [Radeon HD 4350/4550]
vendor: Hynix Semiconductor (Hyundai Electronics)
physical id: 0
bus info: pci@0000:03:00.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
configuration: driver=radeon latency=0
resources: irq:43 memory:d0000000-dfffffff memory:cffe0000-cffeffff ioport:e000(size=256) memory:cffc0000-cffdffff
03:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV710 [Radeon HD 4350/4550]