I got about 8mhz from cooling it on mem and about 30 on core. Mine was getting so hot before that the plastic holding it on had melted and it had slightly brown'ed.
Ive just made a heatsink for the chip thats the perfect size 13mm * 8 mm base made from soldered copper sheet. It has 15 copper fins 45mm long which can be bent out to get mroe air to them. Will try to get a pic of it later once Ive cleaned it up.
Both the tv cards ive had get very hot, infact cooling the tuner chip allowed me to almost watch cable channels whih were previosly scrambled (no decoder box)