I have a powercolour 4870, it overclocks well and runs at 45c idle at 20percent fan speed. They respond to all my questions quickly and seem knowledgeable, i have no problems with them and would use them again.
All the saphire cards ive had have been cheep, but run hot and loud - but there was nothing particularly bad with them.
my HIS ICeQ3 X1950Pro was an awesome card , it was faulty unfortunately (The fan wouldnt start so it overheated before xp even loaded and the pc just shut down) but they replaced it straight the way quibble free and it was great, ran very cool and quiet - can't say i ever tried to overclock it, though.