How to over-ride the autoconfigured Device-section?

[Harald Hannelius]

I'd like to try out a few options for the radeon-driver, but I can't for my 
life figure out why my custom conf-file in /usr/share/X11/xorg.conf.d is 
ignored.

The file looks like this;

# cat 53-radeon.conf
Section "Device"
 	Driver	"radeon"
 	#Identifier "Device0"
 	#Identifier "Configured Video Device"
 	#Identifier "Default Device"
 	Identifier "ATI Radeon HD 5570"
 	#Identifier "RADEON(0)"
 	BusID "PCI:0:1:0:0"
 	#ChipID 0x68d9
 	#disable
 	Option "SwapbuffersWait" "off"
 	# enable
 	Option "ColorTiling"  "on"
 	# enable
 	Option "ColorTiling2D" "on"
EndSection


I seem to be unable to guess at what I should put in the Identifier line so 
these changes get applied. The files gets read, a typo in it will make the 
x-server unstartable.

Please help.