Little tip for you guys if you really want to get the most out of your ATI cards update to 11.6 from debian wheezy and use the following script to setup your cards. You will have to setup your clock speeds to suit you but this works well on most 58XX series cards.

Code:
#!/bin/bash
#globals
CCLOCK="990"
MCLOCK="300"
FANSPEED="80"

sudo aticonfig --od-enable

#More cards ? well add more loops ;) ie; for four cards 0 1 2 3
for i in 0 1; do
  DISPLAY=:0.$i sudo aticonfig --pplib-cmd="set fanspeed 0 $FANSPEED"
  sudo aticonfig --odsc="$CCLOCK,$MCLOCK" --adapter=$1
done
This script will set your fanspeeds to 80% and setup your core clock to 990 and your memory clock to 300 preserving power and keeping your cards a bit cooler considering you will be running them for a while. Let me know how you get on